Stu, just thinking about it all again, I am not sure we talk about the same thing when we talk about decompression plates...

If I understand correctly, when the head is skimmed, it looses a given amount of metal, and the overall depth of the "combustion area" in the head reduces. A decompression plate as I understand it, would recover this depth loss.

Is that what you were on about too ? Cos I can understand how it affects the squish area, but it only brings it back to where it was before the skim