Milling for compression

With the pistons that far down in the cyl, I'm thinking you got a set of the "low compression" pistons, I have seen advertised, online. Measure the distance from the top of the piston to the pin hole, and post it. I have the numbers out in the shop.
PS: The slant six can take milling the head .100 and the block .100, without problems, some have gone even more. There is no way a slant will have quench issues, with a flat top piston, unless the piston comes out the top of the block.