I mounted the trax screen thing where you describe. Against the a pillar on top of the dash right above the driver side a/c vent. When I park in a hotel lot or something I put a baseball cap over it.

I did not look at the 75 gallon tank. The 50 I have I bought off Craig's list here where I live. Paid $400 for it. Still expensive but half of what a new one would be! I did not even know transfer flow existed until I saw the classified ad for it. Looked it up and decided to try it. I really like the trax transfer system. It just gradually pumps fuel as the main tank is drained, doing a good job of keeping the dash fuel gauge accurate considering the sum of 76 gallons. When my dash gauge says 1/2, I actually have 38 gallons of fuel on board.