Sorry for the delay in responding I've been busy.
I should mention that my OPS 30cc calls for 5% castor and thats lots for this motor. When I'm blending fuel for my Rossi's I usually use about 20%.
I buy the methyl hydrate from a local auto parts supplier costs me about $7.50 canadian. And nope thats all I add.
A buddy of mine bought some 5% nitro fuel and we used it. I found my rossi's didn't run near as smooth.
Best thing about mixing your own fuel is that there is nothing to be scared of! It works and its cheaper