I found one answer to this question on another post.  The place around the place where the fill and over flow tubes exit the tank can be reinforced with JB weld or more solder.  I plan to make a support for the tubes near the top where they are filled, probably out of 1/8 or 1/16 ply. 

I think that I remember that the lower tube is the fill tube and the upper one is the overflow.

Allen: I have been flying a Fox 35 powered Brodak Nobler for over ten years using a very simple tank setup.

I use a 3 1/2 ounce tank with one uniflow vent and one standard vent at the forward upper inboard corner of the tank.
I fill it through the uniflow and when fuel comes out the standard vent, I cap off the uniflow vent.
The standard vent is angled forward and has a restricter with an .030 hole.

I have flow it both ways, uniflow and standard; the standard gives the best runs.

Bob Z.