Is it worth while installing a base gasket shim (.059") and cutting the head on a Mxz600. If so does it change operating rpm, also how much can you mill off the head before you have to do anything to the domes? Thanks.

In general, whatever you add to the jug gasket, you should remove from the face of the head. This will net similar compression to stock.

This should add some power to the engine. I have done a couple of 800s, and a 700, but not a 600. Generally, it does not make the engine any peakier than before. On the 800s, it will actually broaden the powerband.