Does anyone know how much compression milling ls6 heads .035 would add?

I computed and came up with 11.9:1, but this was using unmilled heads.

4.1 bore
4.0 stroke
4 cc valve reliefs (i think, there are some reliefs, biggen than an eyebrow size)
ls6 heads
6.125 rods

fwiw the cam is a 110 (+2) lsa.

 

Assuming a stock .thickness .054 head gasket with pistons .007 out of the hole. Milled (.035) LS6 heads apprx. 59cc chambers.

I'm coming up with 12.82