Head skim requirement?

[MA70-3.0GT]

OK so as most people will be aware I have a confirmed BHG on my new toy. So prior to stripping I've just been reading through the TSRM to get an idea of what's required & I noticed that as well as the 58ft/lb error there is no mention of skimming of the head, only that if warpage exceeds 0.10mm or 0.0039" the head should be replaced.

I'm now somewhat confused, I was under the impression that even on a stock composite HG job the head needed skimming lightly to remove any marks left by the previous blow area.

So what I'm after knowing is, provided my head ain't cracked or banana shaped, would it need to be skimmed normally & either way what sort of service limits am I looking at for how much a GTE head can be decked before compressions are too high (and what datum do I take this from?).

I ask because the HG has been done at least once before & not many miles ago, so I'm looking for the previous mistake also & I'm wondering if maybe somehow too much material has come off the head & want to be 250% sure everything's just-so before I put the same head back on, otherwise I'll just transfer the new cams, valves & springs etc to another head & get everything right on the money.