How big of cut to gain 20 psi

[CompKing]

I have a set of one peice head at 33cc and getting 125 comp and just finished breakin.I have a set of 2 peice 2.0 3 1/8 heads that are at 34cc off my last melt down.How much would you cut off the 2 peice ones to get me to the 145 area?

[WATERWINGS]

Both sets of my 2.0 liter (150 and 175) 3-1/8 heads showed 150 PSI on two different comp. guages, on a non ported 2.4