Hate to tell ya Bob, but all pistons are egg-shaped. You should only measure them 10-12mm from the bottom of the skirt and at 90* to the pin axis. As for liner ovality, have no illusions, there is no perfect liner; they are all oval to a small degree, usually around 0.01-0.015mm for new liners (never mind what AR says in their specs). Theoretically, liner ovality should be measured with the liner clamped tight, but that doesn't change much. All in all when you get a new p/l set, I would definitely advise you to check ring end-gaps as I found them too small several times!