I guess your skimming the head for reasoners other than just making sure is flat?
as I've only relay played around with turbo cvh's and skimming the head is only done as a last resort as any removal of head material will up the comp ratio, it's hard to say how much you can safely remove? i would Guess about 1mm ? i could be wrong...? would would have to work out the comp ration with such a reduction as it could become undesirable high...eek

Cheers

Steve