OMG, I don't know where to start, but anyway, the MC28 is just fine to derestrict. If you like the single sided swingarm, then that's the bike for you. Thinning the gasket or milling the heads for a street bike is silly. If you want to race it, then you can think about it. All you're doing is raising the compression and that can be good or bad. It depends on the track and weather conditions that you're racing with. If you're running unleaded fuel, then compression increase can be your enemy so be careful. There are no spacers between the reed cage and case, but you can mill the cases. It's a BIG deal to do, but again, for racing it can be advantageous. The biggest gain in doing so is usually that it allows for greater rpm so you get more power and much more overrev. AGAIN, it's good for racing, bad for the street.

My 2 cents,

Joel