The two configurations (posts #2 and #4) have already been tried. The original configuration was the two line setup shown in post #4. I went to the three line when I realized that I was opening the supply line to the engine every time I refueled... I didn't like that idea, because my filter was on the supply clunk. In any case, this decision had nothing to do with the fuel venting problem, but for the record, the two line setup lost fuel out of the vent just like the three line setup shown in post #2.

The check valve was added later, and has helped the overboard venting problem, so I would like to keep it in the system. I can't see that it could hurt, as it allows air into the tank to replace the fuel pumped out by the engine, but at least slows down the venting losses.

I am going to try Flyfalcon's idea (an overhead loop on the vent line), as mine leaves the tank and immediately dives straight down to the overboard vent tube. I am also going to move the vent line check valve closer to the tank, as it is currently just ahead of the overboard vent. This move would (in my mind, at least ) allow a smaller amount of fuel to be "trapped" in the vent line by the check valve. I suspect the valve lets at least a portion of the trapped fuel out, when it eventually opens to let air in the tank. With or without a check valve, I'm envisioning the vent line being filled with fuel for instance, on a long "braking" downline. Then, when the plane goes upright again, the fuel simply falls out of the line. I'm sure there are other "sloshing" manuever combinations that would allow the same thing to happen. BTW this plane is straight and level exactly twice on every flight; for about 5 seconds after takeoff and for about 15 seconds before landing only .

Now... having said all this, if normal loss is a teaspoon per flight, then I didn't really have a problem to start with. (Of course, that's not what "The Big Boys" told me. ) But if that is the case, I'll simply run a longer vent line, maybe along the curvature of the main gear, to simply keep the gasoline from accumulating on the bottom of the fuse.

Anyway, your time and thoughts are certainly appreciated.

Thanks!