i've been using a 1.8 silvertop block with skimmed pistons, 4wd cossie turbo, efi, ported head etc. and ran it at 23psi without any issues to mention, very strong indeed.
the 2.0 pistons have thinner crowns and are weaker to begin with, early 1.8 pistons have much thicker crowns and are safer to skim.
although i'm building a full zetec turbo engine and selling off the zvh.