How much decking is to much?

dibbons said
Recently re-surfaced deck on two 340 blocks, they both were so far off on the passenger side that it took two cuts just to square that side off. Machine shop told me to order different Cometic gaskets because the passenger side pistons are now .005" popped out further out than the driver's side pistons (.022" vs .017" above deck).

Because unless you are running closed chamber heads the piston should be at least .017 out and another .005 won't kill it.

In reality, the piston needs to be somewhere near .040 out to get a flat top piston to 10.5:1 without cutting the heads to death.