4A-GE engine mix - question

[Uzelac]

Wisecos are very pointed, maybe i could gain another 1ccm only on them . I'm kind of affraid to widen the chamber, area between them looks thin enough already.
Deshrouding valve seats, removing casting marks and cutting down the pistons sounds promising enough, maybe even 3ccm .

btw. what do you reckon, how much skimming head can sustain before it becomes junk? 1.5mm, 2mm, more?
Of course, any head can have valves sinked more and chamber enlarged, but if all that is needed, it sounds too me other head is much better option.
How much is too much to have descent squish with average 1-1.2 mm headgasket?