Well, now I have given it another try, hopefully the last one. By shortening the battens and increasing the AR, I managed to keep the sail area on 40sqm.

The mast balance is now 28.2%. I chose to go back to the 60° yard angle as this pushes the CE a little further forward than with 55° yard.

Personally, I would not be afraid of trying this rig.

Have a look, folks.

Arne

(full size diagram under Arne's sketches, section 8, photo16)

This was difficult.
I found that if  the mast is to go through that hatch, the mast balance in the sail would almost touch 30% to keep the CE of the sail in the same position as in the Bermudan rig.
If the boat were mine, I would be very tempted to try it, but I would not push that sail onto others before it has been tried.
That mast position almost require a SJR rig, which I know too little about.

Arne

PS: Anyway, I let you have a look.

(Full size diagram in Arne's Sketches, section 8, photo 15)

I'm somewhat reluctant to comment on rigs for this boat again, after the way that my suggestions of erring on the side of prudence and good seamanlike sense weren't well received last time; but since my name has been mentioned, perhaps I should.

The problem with a Badger-like rig on this boat is that when the mainsail area decreases relative to the foresail area, both masts need to move aft in the boat. I think that the mainmast is likely to clash with the sliding main hatch. A PJR distribution of sail areas, 67/33, would seem to put the mainmast just forward of this interference, with the smaller foremast being well forward and clear of the V berths. This is a practical possibility.

Yet I would question whether it's necessary to go for a schooner rig. 450 sq ft in a single sail, on a mast stepped through the forehatch area, seems to be reasonable and practical, without impacting the accommodation too badly. I think I'd favour it, using one of the 40ft hurricane-proof flagpoles you mention. Possibly the 8 inch thicker-walled variant (subject to verifying by calculation)?

The Alberg 30 was actually discussed four years ago.

The Junk Rig Association - Alberg 30 Conversion Viability

Arne

There are many men and women on this forum that will be able to help you and point you in the right direction, however technical rig design is not my strength, so my contribution to your exciting decision is that the Alberg 30 is one of my very favourite boats, and if they had any in NZ I would have purchased one to convert.  Instead, I found an equally classic design as in a Twister 28, same heavy displacement type of old fashioned classic plastic boat with folkboat roots of the 60's and 70's.  I really hope you do go through with it, it will be the best decision of your life in regards choosing a junk rig for an Alberg, and all the hard work when you splash and sail your junked rig Alberg will be worth it.  Go well.