Over the years I have run 4 different fuels through Saito 72's. Three of those had castor in them. Nitro was anywhere from 15% to 30%. While the tune was effected by the higher nitro I pretty much ran what was in the jug with no issues. I never had any valve issues with the castor blended fuels, but it will tirn the mufflers and headers dark brown. BTW the APC 13x6 is a the benchmark prop for these.

david