I mix my own glow fuel, and have done so for 30 years, the only thing with straight castor and 4 strokes is it requires more maintenance due to carbon build up around the exhaust port and piston ring. With regards to performance, I find that all of my engines run better on 100% castor lube fuels, though I don't have any exotic type engines, i.e. no ABC, ABN, and AAC. In fact Ken Enya still recommends a straight caster oil fuel mix for all his engines including 4 strokes. The nitro content will give you more drama though, you may need to increase the compression and or use a hotter plug for a reliable idle, and most carbies are set up for nitro so it will have a negative effect on the low to high speed transition.

This is an old Enya 46-4C with 10% nitro and nil nitro, but both are running straight castor oil...

http://www.youtube.com/watch?v=xHYmE4NGEzY

http://www.youtube.com/watch?v=O6q358B260I