Oversize (letter?) piston for plated bore?

[YELLOWSTREAK]

My '98 RMX250 is showing a bit of wear in the plated cylinder. Imagine that! The factory service manual calls for 67.000-67.015 mm and a very qualified machinist measures mine at 67.020. Otherwise, the bore (and for that matter, the standard size Wiseco and rings that came out) look really good. My question: Go back with another standard Wiseco as my buddy recommends, or one of the slightly oversize kits from Pro X? If the latter, how do I choose the (letter?) oversize? This time, I plan to bump the compression a tad with the optional thinner head gasket, if that makes any difference to anyone. Thanks in advance for the replies. I love this place!

 

[CRguyStan]

If you look at the Pro-X book at a dealer it has the actual dimensions, or did the last time I used one. I was able to sacrifice a worn jug for a few more pistons with them.
Stan