i wouldn't do it that way, not any lower than 4mm off the skirts of the piston crown.
then i would take 3 mm off the block

That will give you another 7cc, or if you take 4mm off the block = 13.6cc lost.


then how much can you remove off the head? as the piston would be just under flush with the block now (with 4 off piston, and 3mm off block),
then you got 1 - 1.3mm for head gasket.


also a std cossie bore is 90.82mm