Aeronut, sorry, missed your question. I think more compression will help. I don't use a base gasket on my engines. I use a sealer called Yamabond from the motorcycle shop. It's for crankcase halves on motorcycle engines that don't have a gasket. Works great. You can measure the compressed gasket thickness, and take that much off the top of the exhaust port to regain the exhaust timing. When doing this, you need to also check your deck clearance. (Piston to head clearance.) To do this, just insert a piece of rosin core electrical solder into the spark plug hole, and turn the engine over so that the piston crushes the solder flat against the cylinder head. Then measure the solder to get the deck clearance. You want about .016 minimum. Be sure the solder reaches all the way over against the cylinder wall, as many engines have a raised area in the head at the outer circumference called a "squish band". We often machine these out to be able to lower the cylinder as much as we want to, but most often you can get away with the "leave the gasket out" trick without having to do this.

Good luck,
AV8TOR