0.5mm is for 16v only.
not sure of the raise in compression, i don't trust my maths that much. but if you want to work it out, the stock gasket is 1.2mm. both measurements are when torqued up.
i have a mate with an n/a smallport that pushes out over 200hp, to do that they FILLED in a small port head....
the ports in a bigport are HUGE, thats a hell of a lot of airflow.... i know of plenty of 4agtes with over 250hp, and most if not all iknow of first hand use 20v or small port heads.
thats not to say you can't make that power with a bigport....
one thing i do know is, the secret is compression, and you seem to be on to that :)