The large Mokis (120-210) are fine "European" style engines. Their high compression mandates low nitro and their long induction timing spits a lot of fuel. Adding a head gasket and using 15% nitro will make the needle and tank size/location noticeably less critical while adding power. Propping for higher rpm will also unleash some power and help with fuel draw. Good muffler pressure, plenty of rpm, and a small well placed tank are the keys to reliability.