I'm only developing the twin-6"50cal as a new product. However, in my desire not to leave my Airfix Belfast kit short of any turret(s), I molded one to make resin copies for bashing, etc., and have already cranked out several! None of them are perfect - all having a pit or two here and there - but nothing an accomplished HobbyHorse like yourself couldn't handle.
So, if they're big enough for you I can set you up with 3 or 4 for just the cost of postage, John! Howzzat sound. buddy?