The unaltered piston has a compression spec of 9.9 at 62cc of chamber volume. Your pistons have had the step dome REMOVED, so you are a good bit lower than 9.9.
Put this stupidness to rest. CALL United Engine And Machine. Tell them what you have and they can probably tell you almost to the n'th degree what your compression is. My guess is it will be around 9:1, possibly under 9. CALL THEM!
