if theres a perfect seal between the head and gasket (which i think is impossible to get a PERFECT seal) then im guessing no need la... but then again u have to keep in mind that the valves and piston heads will also be close to each other and possibly collide. aint too sure of this myself...but its still a possibility.

also take note that if u increase ur compression ratio too high u wont be able to use normal fuel...u might end up having to use racing fuel coz ull need the MUCH higher octane. i think that point would be somewhere around 13 if im not mistaken