Ryan, apart from the mast's relationship to interior accommodation and deck structures, the other reason why it might be desirable in some cases to prefer the mast further aft is to do with distribution of weight. The rate and extent of pitching can be affected by a mast which is too heavy and too far forward on a boat without enough buoyancy in the forward sections to accommodate it. As Arne has pointed out, this should not be an issue in your boat.
I will chime in here on the question of balance. It has sometimes been a controversial subject but in my view it need not be.
The balance referred to is aerodynamic balance, that is, the ratio of the area of that part of the sail ahead of the mast centreline, to the total area of the sail. In a split sail, the area calculation includes the area of the slot. A convenient estimate which is good enough in practice is to simply look at the ratio in which the mast divides one of the lower battens.
There is a limit to the balance which can be given to a junk sail, and this limit depends on whether it is split or contiguous, and also on the shape (eg yard angle) of a contiguous sail. The significance of too much balance in the split rig is that the sail might not weather-cock or automatically depower when the sheets are released. In the contiguous rigs, I am told that the mast will interfere too much with the shape of the sail if the balance is too great, but if a better explanation is required it would be best if the designers of the various contemporary rigs were to each explain where the balance limits of their respective rigs lie, and why. Also, these matters have been discussed in other forum threads in the past.
The split sails are invariably given the highest balance (indeed there would be little point in the split if the balance were very low.) A by-product of balance is that it determines where the mast needs to be placed. Split rigs such as SJR and the aerojunk rigs lead to the mast being placed further aft than the contiguous rigs, as you will have seen already from this discussion. Each of the rigs has its own set of advantages and disadvantages and each has its following.
Sometimes a junk rig conversion leaves the owner with little choice about where the mast should be placed, because of internal accommodation arrangements or (less usually) concern about weight distribution. Arne has already explained that this latter concern should not be a problem in your case. More likely the things for you to consider will be internal accommodation arrangements and/or deck structures which may be inconvenient in relation to the new mast position. By reverse reasoning, if there are restrictions on where you can place the mast, then this business of balance could determine the type of rig you will choose.
If you are free of any restrictions as to where the mast can go, then you can move on to the interesting question of which rig is “best” and this is where the various afficianados will disagree. For coastal cruising you can be assured that all the contemporary rigs are good, each in their own way. Fortunately for us, each of the people who have most been credited with the development of these cotemporary rigs has been extremely helpful in giving advice on their particular developments, so whichever rig you choose you will most likely be given the all help you will need – an enormous advantage of being a member of the Junk Rig Association.
The implications of aerodynamic balance (the question which you have raised), is probably not of huge importance provided you are within the range of balance which suits the rig in question. A sail which is large (relative to the boat) and wide, will be mostly out to one side when running down wind. If the balance is low, then this “all out to one side” characteristic will be even greater. If the boat does not steer well, this could be a problem, though there are various remedies. Also more force will be needed on the sheet, to pull the sail in and out. So one might reason that a sail with high balance (like SJR) might be more suitable, or a sail which is tall and narrow. At the end of the day, however, these are not rules or imperatives, not necessarily a serious problem, and there are other considerations. Hull shape, rudder etc are far more important co-factors. The rig sometimes needs to suit the boat, but you have a hull which should answer very nicely to whatever rig you choose. I sailed recently on a Contessa 26 which has a hull, I would say, slightly finer than yours but very similar in many respects. (It was Pango. see front cover of recent JR magazine.) Quite similar to Arne’s Ingeborg. We carried a big, wide, heavily cambered, low aspect ratio sail with not a lot of balance – and yet the boat handled beautifully on all points of sail. I do not think you should get too hung up on the handling characteristics of the various rigs, as your boat will handle beautifully anyway, as long as you follow sound advice relating to your rig of choice.
My rig of choice for my little boat is the Amiina-style SJR (for none of the reasons discussed above), with the top panel unsplit, and I am very happy with it. It has a balance of 33% as it was designed to have, and it is not a race boat. That figure suits the split junk rig as a coastal cruising boat, as has been demonstrated so many times now that it can be regarded as beyond any need for further discussion. David, who has accumulated a wide and deep experience as an ocean mariner (and as a sail maker) has speculated that this figure might be a little on the high side for an ocean cruising boat, and the response to your invitation to David to explain why that might be so, will be of some interest to all of us. Pete Hill has extensively voyaged successfully with a split rig (aerojunk) which suggests that David is perhaps being a little conservative, but that is the result of his own hard-earned experience as a pioneer. For those of us who are less experienced and less fitted to be pioneers, David has quite properly pointed out that to date, no major ocean voyaging has been done with a SJR.
David has also hinted at some inherent weakness in the SJR though none has been reported so far by anyone who has actually owned one. The jibs do not have any particular tendency to “flutter or flog” (mine don’t anyway). They don’t need battens and I would not put battens on mine. There is, however, no arguing with David’s insistence that a sail for ocean cruising should be stoutly and soundly built to withstand heavy-duty and continuous use.
In my humble opinion you are in the fortunate position of having a boat which will respond well to whatever rig you place in it, and you can simply follow your heart, and be concerned mainly with what changes you are willing to make to your internal accommodation and deck structures. You mentioned sail area, and if that is desirable for you, then the Johanna style seems to give significantly greater sail area for a given length of mast, than the other contemporary rigs. Good luck. Lovely boat.
Edit: Slieve's post popped up while this was being written. Slieve, great to see you back in the forum and keeping a watchful eye. (And to see that lovely avatar - the Poppy sail being the most beautiful of all the junk sail forms, to my eye.) Yes, in that rough diagram I made the sail areas perhaps too small - and also placed the rigs a bit too low, not enough deck clearance. Sorry about that. It was just a quick stab to see roughly where the mast placements would be.
PS If we are lucky we might soon see some details of a boat in Whangarei which has recently been fitted with a SJR with a balance of 30 percent (or less?). I believe interior accommodation was a factor in the choice. Word of mouth reports so far are favourable. This will add more to the body of practical experience which has been documented so far.