Colin.
Peter Cockerton's 'Joybells' is the only BR20 I know of that has a bermudan rig.
My own WE BR20 'Psalter' that I owned until a few years ago had the standard BR gunter rig (I may be wrong, but I think the BR20 is a gunter as opposed to a gaff?).
Hence I, as Peter does as well, have a lot of experience in sailing both. I would say his bermudan was superior in a lot of aspects, obviously particularly when beating, and it was marginal on a run or a reach which one was better, not a lot in it at all. The sail shape he achieved was always leaps and bounds better than anything I achieved when set - the notorious leach flutter was all but impossible for me to eliminate.
Sail handling was maybe not so easy - reefing and furling, but Peter would have to comment on that. But I would say though that now I have the BC23, with the bermudan sail, handling it ie, hoisting , dropping, reefing etc is very easy. But I have lazy jacks and a sail bag to drop it into. I do of course have a track up my cf mast that I 'lubricate' regularly with silicon spray - so my main slides up and down like the proverbial on pay day.
The only major drawback was having a full length mast that could not stay in the tabernacle when trailing - but that is the same for the BRe and the BC's anyway.
Peter has a wooden mast, which is heavier but certainly manageable by one man, as Peter will no doubt testify to.
Your mast would have to be the same length as the boat (20') for trailing.
I'm aware Peter got a bermudan main sail new from Hyde especially for the BR20. So they are out there.
Personally, in my experience, I think it is definitely a positive move and opens up all sorts of avenues in sail shape, 'fat' headed? Fully battened?.. Laminate?..
I'm sure more knowledgeable people than me may differ ... ?!
Love to see how you get on with this project if you go for it..
Andy