I have an early Supersport Custom, which was a special model BSA did, it has the Superstar trigger, barrel hinge bolt and lovely beech stock like what they fitted to the Super/Goldstars with checkering and high cheek piece, I've fitted a true .25 barrel to mine (not the early tight .243 barrels) and just fitted some delrin guides to the original spring, it shoots nice, it still has a bit if recoil and I'm sure it could perform better with a proper tune but I just enjoy shooting it as it is at the moment, I may get it looked at in the future.
Pete