Personal preference was all, I just like it with turn downs. I thought about going out in front of the rear tires, but I've had cars with that arrangement and it's really hard on aluminum rear wheels. I didn't want full tailpipes because of the rear mounted tank, and didn't want interference if it needed to be removed. So yes, I do have a custom 33 gallon Rock Valley tank mounted behind the axle. At the time I designed the tank this was a long distance freeway commuter. Having lived through the gas shortage period of the 70's, I wanted the biggest capacity I could fit in the space available (limited trips to the pump). It tucks up nicely, but if I had it to do over, I'd go for something closer to 20 gallons. Now that I'm retired it takes a long time to use up a full tank of gas. Here's a shot of how well the tank fits, so full tailpipes would have fit okay:
