WHy have a pump !! I have a prototype of a ZIMPRO 91 size Viper using a OS 91 fx 2 stroke engine swinging a 15x10 apc prop at 8800 rpm with out of site vertical.. The plane weight is 7# 6 oz and the fuel tank is on the CG and only using pipe pressure !! The plane was designed for the ys 91 and since the engine is hard to come by and the simple 2 stroke set up, thats why this test was done.. Dennis also has carbom fiber option which would also make plane lighter.. We are using a MAC's quiet pipe and a karl M. header.. see photo of the 2 OS 91 vipers... Mine is the red/white/blue.. I dont see the need for the pump with this set up..

Scott