Davidd, I don´t mind having all sorts of components in my bikes, no matter where they come from or if someone else does same. The B-Rapide engines have Alfa Romeo pistons plus 4mm compression plates under cylinders now. The pistons in my photo are Porsche cast iron cylinder types and go in the BMW alu pots so I coated them for less cold clearance . . . . after I had to hone the BMW cylinders a bit oversize because of seizures at both sides . . . . . ahmmm, because I forgot to fill in any oil again when I changed all oils on the bike, engine, gearbox, swing arm, rear bevel drive. But no oil in the engine so it lasted 17 kilometers (11 miles) from home till I felt the seizure and stopped. Sent my lady back home to get some liters of engine oil with the car and filled the engine at last . So I laid the flat twin on both sides to soak the pistons, kicked it and got home with no morte troubles. But the nice set of pistons were scrap.
I looked at the piston photo you posted , Manx type. The installed piston in the cylinder does not look as dramatic as the special high skirt new piston. But anyway, you´d have to machine the Vincent head a lot to clear this piston - unfortunately just at places you´d NOT like to have weaker than standard. I learned in the forum that Vincent heads tend to be somewhat flexible in the middle and weakening this place seems no good idea for durable use, racing allright, I´d think. Is there somebody with pictures of a Vincent head showing this mod ?
Vic