Is this for an RV type of aircraft ??
You mentioned that it was a low wing. Earlier RV-3 used a header tank, -4, -6, -7, -8, -9, -10 use wing tanks, and the -12 has a single high tank aft of the seats (could this be called a header tank??)
Sloshing of the fuel in the tank(s) that would un-port the fuel pickup is not an issue in coordinated flight. Other maneuvers that embrace skids, slips, and inverted flight are another matter. And for these aerobatic kinds of maneuvers, a flop tube in a header tank may work just as effectively as a flop tube in a wing tank.