Edward, that sounds good.
The Splinters, with their masthead Bm rigs, will be slowed down a lot in the 100° wide downwind zone without spinnakers, so a good junkrig should win almost every time against them, with that handicap.
It is much harder to put a JR on a Nordic Folkboat and expect to win over the originals (same sail area). The Bm-rigged FB has over 70% of her area in the mainsail so does a lot better downwind than masthead-rigged boats. In addition the shape of the main can be tuned for racing, much like on the modern racers. I would of course give a FB a much larger JR than the original 24sqm - say 36-37sqm - but then I am not racing ...
Back in 1995 a Swede contacted me. He and a friend had a 34’ steel Bm ketch. When replacing that rig with a cambered panel JR (not bigger than the ketch) the ship was transformed and went faster on all legs. So to rub it in; a BM rig that is not tip top is easy to beat. The fleet of modern racers that Ketil has to race against is a much bigger challenge.
Anyway, good luck!
Cheers, Arne