I Did note in my first post that no the two ounce differance in itself may not be a big issue but it is common for new folks to get carried away on tank size and thats the point I wished to raise.

Ray your figures do make the point yourself that the larger a tank and the wider the spread is from full to empty then the headpressure change is even greater than with a smaller tank. The needle valve must deal with this change from full to empty or there will be running problems.

Granted this is only one of the involved varibles effecting an engine run with the muffler pressure also a varible as well as flight loads and the fuel tank spray bar relationship.

Don,t get me wrong although for most of my sport glow flying I use smaller tanks than most for the more uniform runs from full to empty that can be the result but I do on occassion have some silly setups. Just this morning I completed a two hour and three minute flight with a .70FS powered airplane and most of 56 ounces of fuel.

John