Update on my fuel venting problem.
originally my vent pipe ran from the bung in the DuBro tank to a simple nipple in the fuselage bottom. I used the small Tygon tube. In the photo below the vent tube is behind those wires.


Following your suggestions, I added about 15" of the larger Tygon and looped it up and around, and down to a forward-facing vent.



That seemed to cure the venting. However I cut the extension much shorter, only 5" or 6" extra Tygon, but still looped it up high, and that worked fine too, still no sign of venting.


Then I tried looping the excess down and around, and still it wasn't visibly venting, but looked neater.

So my next step is to replace the tape covering the U/C wire which has been discoloured by the venting fuel and oil and see if I have cured the problem long-term. Thanks for the advice/suggestions.