The pistons don't have valve reliefs, they are flat with a slight dish so not a problem on this engine but most valve reliefs are usually spec'd for what ever size valve they fit or for stock size valves.
But not all. If its a custom piston the configuration could be tight in this area. In your case this method wouldn't worry me. But I wouldn't use this method ( or dial indicator either) as gospel. Especially if cam timing may be moved around. Doug
