Good point on the flow check as it comes out of the valve. My question relates to a helicopter so climes are rather flat, none the less these are all valid points.This system seems to work just don't want to take things for granted.I would check the fuel flow out of the carb with the bowl removed to open the needle valve. The needle valve may be the smallest restriction and a large fuel line won't help if the pressure (fuel head) isn't sufficient to flow past the restriction.
Thanks,Tanks over the engine can't get much better gravity wise. What you want to check is if one tank will feed. I know a couple of cases where one tank got clogged so only one was feeding the engine. They were helicopters. Also check with minimum fuel not full; the extra fuel weight helps flow, you want worse case. Depends on engine and its needs. The Enstrom helicopters I mess with have -8 lines I think.