Anyone here ever have their pistons machined?

I don't think you would have to deck the block. Just mill the pistons. This is assuming you have domed pistons that stick above the deck. You would mill the pistons down to deck height.

***Edit*** I just read the op again and see where he mentions milling the deck. First, if you mill the pistons to lower compression you will gain it back, at least partially, by milling the deck.

How about more info on your build, such as timing, deck height, pistons, heads, current quench, gasket thickness, and current compression ratio. Thanks.