id go the 17:1 jeremy i rekon it is tried & tested so stick to somthing ya know will work
the other thing is see if RD or dazza can round up a 44mm Wiseco piston from memory
ozminimoto had a a few with the blata rep big bores kits they were selling if not try to round up a quality set of rings not the chinese rings ??
i have came across a ac cag that i was put a headkit on for a bloke it seemd to have a flat top style piston but it was probbly a chainsaw piston or somthing that had the same measurements as the chinese cag ones
the bore was worn & the bike wasnt running so that could have been the reason lol