After researching it a bit more, it appears that the CR250 should have somewhere in the neighborhood of .85 to 1mm, or about .040 to .055 when using pump gas.
The RM65 should have .27, though .28 to .35 is ok, with a compression reading of about 155 to 160.
Getting specifics on KTM stuff seems pretty easy, it's the other brands that getting info for is a little bit more difficult.
The general consensus that I've seen is to make sure the correct squish angles/length are still achieved after milling, and to make sure the combustion chamber is the right size too. Seems that when more low-end is desired, milling the bottom of the cylinder is preferred over milling the head, as it lowers the ports slightly in addition to bumping the compression and improving the squish.
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