I always thought the return needed to be as far away from the fuel leaving the tank to where it has additional time to cool before reaching the outlet again. If you look at most fuel cells the returns are on the top , as far away from the outlet as possible . If returned next to the outlet you wind up sending warm fuel right back out and after x amount of re circulation cycles you have hot fuel .
On a truck/car that sees mainly one direction of travel and doesnt use a sump, you can get away with this. Really, your still putting warm fuel in a tank that cant cool its self so no matter where you put the warm fuel in, its going to heat the tank up. A good fuel cooler will will negate the whole issue. driving around town these last few days ive yet to see fuel temps over 100*.
not having the return fuel go to the sump means you solely rely on what fuel is caught in the sump to be used. when the tank gets low and fuel starts sloshing around more and you take hard long corners that drives fuel away from sump, you can actually suck the sump low enough to get some air. If you run the return to the sump, it will help keep some fuel in the sump to draw from in extreme conditions.
I know alot of you are looking at a drag race situation only. I have needed to look at all aspects for desert racing or duning. On a street truck it may not be as extreme as im making it sound but why have to worry about air if you can solve it with a little planning, not to metion if you want to use the full capacity of the fuel cell, why have to fill up when ever you hit 1/4-1/2 tank every time. I hate having to adjust driving style around a part cause it didnt work as well as the stock engineered setup did in a stock truck.