Here's my tuppence worth. The most excellent thing about a junk rig is not just the ease of reefing and handing the sail, but the complete elimination of jibs, staysails etc. There is simply nothing needed to do when when tacking other than put your coffee down somewhere it won't spill and just steer onto the next course, no sheeting of flapping jibs and you hardly even lose way. This is one of the reasons for these impressive GPS track recordings of tacking up a narrow channel. which we have been seeing recently on the forum. It is an understatement to say that a junk rig is almost as good as a bermudan rig upwind. In a confined channel it is far superior, which is why junk rigged boats are almost the only vessels you ever see tacking up a channel these days.
You could do a proper junk rig conversion in such a way that you could always go back to the original rig, not that you ever will, but if perhaps it helps resale at some later point. I think it is wise to keep this in mind, but in the meantime don't compromise. (I have to disagree a little with Jan, here)
I can't find a sail plan drawing to be sure of the following, but here is what it looks like. You need the mast to be near to the original mast position, or be able to move the mast position forward to the next bulkhead position, because you will want some decent knees or a beefed up bulkhead to support the deck and partners, which will bear the loading of the free standing mast. It looks as though the fore-triangle is very small on this sail plan (from what little I can find) and it is possible that you might be in the rare situation where a high-balance (33%) sail might just have a geometric centre (centre of area) which matches the centre of area of the bermudan rig. That would suggest your best bet would be a split junk rig on the original mast position. It's an uncommon situation but a possibility, do the maths and have a look at that possibility first.
Next option (and probably the more likely scenario) would be to beef up the bulkhead and deck to form partners and mast step for a free standing mast, offset, on one side of the companionway. That sets the mast a little forward of its current position and could perhaps still match a fairly high balance junk sail.
Third option would be to move the mast forward so it can exit through the existing hatch and at a guess a lower balance junk rig would go there, but it seems to me more structural modifications to the deck and hull would be necessary than in the case of the previous two options in that case. Furthermore, you lose your hatch.
You could probably make a viable sail plan with the mast just ahead of the hatch and very high low balance rig. I personally prefer to see a mast as far aft as possible
That's just based on the only two diagrams I could find. If you have the original sail plan I am sure someone could design a junk sail for you which would match the original sail plan in terms of helm balance, and I am also sure that converting back to the original rig would in any of these cases be quite feasible should you choose to do so, especially in the case of one of the first two options, less so in the case of the third. (And its not a silly idea to keep re-conversion in mind. I sold my original rig and regret it now because I would like to sell the boat but I would prefer not to part with my junk rig).
While typing this I see Arne has got interested. I bet Arne could point you to a sail plan which would be very hard to resist. Be sure, as a starting point, to read Arne's notes in the Members Area/Documents/Technical Articles/Arne's Files section of this website.
