We're not that familiar with nitro-benzene, other than it's not good for you. Check in the fuels section, I think it's been discussed before.

Actually, though, you really don't need nitromethane at all. 20% oil and 80% methanol will work nicely. Use an O.S. Type F plug, and the engine will be fine. You'll sacrifice a small amount of top-end power, and a few hundred RPM at idle, but the engines have been well-proven on no-nitro fuels.