25 ounces a minute is hell to move it'nt it?

On the P200 powered Lightning Roger has, we were able to get away with all fuel fitting being at least a 4mm diameter inside dimention.

I have not seen the tanks of a UB, but if they are using bv's insert type fuel fitting, those are .094 diameter, and therein lies probably all of your problems (I think). Air is so easy to move, but the pump is able to move fuel out of your UAT faster than your other tanks can feed it. (again, I'm guessing on the BV fuel fittings.

This site I use commonly for machining http://www.madison.k12.wi.us/toki/teched/codrills.htm indicates that .094 is 2.4 mm. A serious bottleneck, or in fluid talk "feet of head, differential pressure, etc".

Anyway, if I'm way off here, I apoligize, but certainly having dual inputs to the UAT is going to help keep it full, but if the small oriface for moving fuel is your problem, you also have to keep in mind head pressure to the pump to draw the additional lines, T's etc. Also have a harder chance of getting perfectly even draw through everything.

Anyway, the fitting was my first thought.