Boost after .020 head mill
 

I got AHP stage 4 heads with a mill of .020 and a mild cam. I dont really care for the cam and I am thinking about going E-Force or Maggie. Is a .020 mill gonna grenade my motor? Is a thicker head gasket ok?

Thicker head gasket is fine but you are loosing a little clamping force is run e85 studs and 800whp max 750 to be conservative tbh

I think there is more to it than that, you should talk to an engine builder with experience in the matter. I only know enough to be dangerous, but knowing your quench will help figure out how prone to detonation your combo may be. There are scenarios where more compression with proper quench will be much less prone to detonation. Consult with a reputable builder/shop that can attend to your plans.

feed it heavy methanol to fight detonation too

Just find a good tuner and run e85 meth also if you can swing both 750whp should be plenty safe if you keep the chambers cold with the e85 many have ran 800whp on meth and gas and raised compression. Biggest issue other than guides is the ring lands they butt and break pistons and sleeves at the same time next weak link is pistons then sleeves. Was told sleeves like to shift around 750-800whp just have some arp studs and a thicker gasket to try to drop to stock or lower than stock compression