i have the tanks PA series module (a little different than the GPA). I don't like the fact (at least with the PA), the AN fittings can hit the screw heads and interfere (can't quite turn things to avoid it). That's with AN-8 fittings.
also, just because it's in tank, doesn't mean the pump is submerged. you need to have a well filled tank for that to occur.
also, in tank may help keep the pump cooler (if you have enough fuel in the tank), but you also have a great heat source inside the tank and heating up the fuel that surrounds it. the longer the trip, the more the fuel in the tank will heat up (of course external ambient temps and the tank thermal impedance can delay it). in addition because it's returning fuel from the hot engine compartment, that can heat up the fuel in the tank as well. basically, don't assume putting a pump in the tank prevents fuel temp/cavitation issues.