All my pistons were bigger than that by a considerable amount. In fact, two of them were over the stated maximum size for the group, although they were all from a group 1 engine.

Here's a spreadsheet I made to track my dimensions: https://docs.google.com/spreadsheets...it?usp=sharing

Just a thought: Are you measuring in the right place? Spec says to measure the bore ~65mm from upper edge, traverse to engine block, with the crank girdle mounted and tighten to spec. Pistons are measured ~62mm down from piston crown, 90deg offset from pin axis.

 

Wonder if they tend to go oval with use. What other ways are there for them to end up bigger than they were when new=