Milling crankcase deck surface – How much?

How much metal can be cut off from a stock UL crankcase deck surface without having a major manifold alignment problem. I’m trying to set the squish at 0.045-0.05 but I don’t want to mill the top of the cylinders, because both cylinders had already been nicely relieved and polished. Any suggestions?

Mill the base of the cylinders.

Thanks for the reply. But my dilemma still remains unsolved. As far as I know, milling the base of the cylinder will also affect the manifold alignment in the same extent. In order to reach 0.045 squish I must cut off 0.05 (crankcase deck or cylinder base). If I do so, will I need a custom manifold?
Thanks.
Helsingborg.

No, most manifolds are slightly loose, and the relationship isn't linear.
At worst you just file the ends of the legs slightly.

Thanks Panic! and Chris!
Helsingborg.