I bought an Aero DP-45, 45 Gallon, Alum. Tread-Plate, In-the-bed tank about 6,000 miles ago. I like the tank a lot. It seems well built, and is a true Aux. tank, not a transfer tank, although I use it like a transfer tank.
I have a couple of gripes about Aero. (1) When I bought my tank they wanted to give me one off the showroom floor, and I looked it over and decided it had way too much dust in the bottom from sitting there with the filler and gauge holes untaped. I asked for a fresh one from the back. They brought one out, and the holes were un-taped on it too, so I just washed it out with #2 before I installed it. No big deal, but I guess I expected more cleanliness since we are dealing with a Diesel Fuel System here. (I put a NAPA fuel filter/separator in line and now I filter most of my fuel twice).
(2) I've had a hard time finding a locking tank cap which won't leak. I finally just used the non-locking one that Aero gave me with the tank and it doesn't leak, but won't lock either. I'm working on that one.
Overall I love the tank, and it is very slowly paying itself off. I'd do it again.