We've run the O.S. Max .91 FX on fuels with 5%-15% nitro with no problems. It amounts to how well you have the engine set.

As far as fuel line is concerned, we use standard size, but the tank's close to the engine. If you have a long run, then you may wish to go with larger fuel line. It all depends upon the particular installation. If you have a fuel-draw difficulty, larger fuel lines may help.