It is better to run a flat top piston than to use a domed piston.
I had used 307 forged flat top pistons w/4 valve reliefs & had 12.0 compression.
If you need a domed piston, run as small of a dome as possible thats needed to get your compression.
A domed piston hurts the flame travel.
Keep your quench tight & as big as possible..
If you are running the Brazillian 12 port head the combustion chambers are a lot smaller to begin with as compared to the siamessed cyl head. IIRC.
