A stock RST is not 8.2:1 it's 8.5:1 and there is no problem running at 9.0:1 with forged pistons/rods, good mapping and 99RON fuel, plenty of big power cars running that sort of CR, Stu Collins and myself for example, I ran 30psi circa 280bhp and Stu makes another 100bhp on top of what I did
IMO the chances of a Cometic multi layer steel gasket failing if the block/head have been decked/skimed and is torqued down correctly are very low, you would need some serious heat to do that.

For the OP's target power of 300bhp I think it will be 100% spot on, will be a nice responsive engine with the right turbo

Also just to add... My current ZT build is 8.9:1 running a bar, 95ron fuel and there is still plenty of boost and advance to dial in when my new manifold is finished