Don't bother with 87.5mm pistons unless your going with liners, its even reconned that 87mm should be used with liners as the standard liners aren't very thick in the first place :shock:
Also if Dave does another picture with the gasket removed you'll see another reason (between the cylinders) not to bore to big
As for 94mm bore even with liners :shock: wouldn't hold out much hope for the engine at high bhp levels, theres not exactly alot of room between cylinders as there is with out another 8mm being removed :!:
Also bigger pistons means heavier pistons which will affect how the engine revs going bigger with pistons isn't always the way to go, some engines actually make more power by reducing the piston size as they can now rev better and so produce better power all be it higher up the rev range.