Mike and Tony are correct, and to Tony’s point, a thinner gasket/tighter squish will lower your exhaust port and retard timing a bit. Yes, you will get more compression, but with a lower exhaust port, you will be moving the engine’s peak hp to a lower rpm band. So, if anything, tightening the squish in the absence of any other adjustment will give you more bottom and mid and hurt your top end. You should be targeting 15k in a Rok, so you aren’t far off. Just add a tooth on the rear.