Polini 221 squish and gearing

I've fitted a polini 221 measured squish with head gasket fitted and is 2.2mm ? Is it better without head gasket or with? Seems very large

What gearing are you using, currently I have 23/65 with t5 forth gear, but find it very revvy , would it be better with standard p200 forth? I'm also thinking of changing exhaust to sip/jl right hand exhaust to help stop it revving too early , any help appreciated