I am in the same situation as you. My GX head has been milled so much [to run methanol] that I now need to drop the compression ratio.
For me the best, cheapest option is a thick head gasket, the other option is if I run a different head with a different manifold with different carbs.....this all costs extra money though.
Just out of curiosity, what is your compression ratio at the moment? Also, what is the volume of the combustion chamber [cc]. Reason I ask is; you may want to consider 'opening' up the combustion chambers to a larger capacity, that is what I am considering, instead of the thick gasket [and all the sealing issues].
Other option is using a high octane fuel. Do you guys have ethanol blend fuels in SAfrica?