Hi Steve,

Won't be so bold to say I know the answer; but - it sounds like the right tank fuel line may have some intermittent restriction.

FYI - sitting level, our 13 gallon fuel tanks came up to about a pint unusable on each side.

A couple questions

1) Do you have anything, like a filter, or strainer, in either line going from the wing tanks to the header tanks? If you do - I'll confess my experience with this issue....

2) What design valves do you have in the tank lines? Are they a smaller ID than the lines?

3) Is there any possibility of a flap of material or something else floating around in the header vent line or the right wing tank line; or, any possibility that the fuel line has swelled partially shut on the inside where you cannot see it?

4) Do the fuel lines and header tank lines avoid any loops?

Sincerely,

Dave s