that's really odd on the piston clearance. i just finished a combo with 4.600 bore and those pistons only needed .0065 clearance. the 4.375 pistons i put in a combo last week only called for .0045 and the current combo with 4.625 bore only calls for .0065. not sure why a 4.350 bore would need that much clearance with 2618 pistons. i guess i'll take your word for it if that's what was on the spec sheet. just seems like a lot to me and i probably would've questioned Diamond on that one.