found this lurking on the shelf from 2005, sort of got over shadowed by my my Irvine 53s, the JEN 56 from Just engines UK, same as the SKs I think, it is ABC it is now replaced by the JEN 57 which is ringed is the current production, will give it a shot in the next few days and see how it compares to the Irvine 53 conversion martin
It did pop right off on a few drops down the carb and a couple of flips, great compression