I have never heard of anyone NOT using a UAT or hopper tank. I certainly wouldn't!

The fuel gets sloshed around pretty good during flight with the type of flying we like to do. So it is not unusual for a bubble or two making their way through to the UAT during flight. I saw one fellow forget to refuel after a flight and went up for a second flight. He shut down after taxiing back to the pits and both the tank and UAT were bone dry! He must have used all but a couple of molecules of fuel during that second flight....! But the turbine kept running on bubbleless fuel til he shut it down. That was as convincing a demonstration as you could ask for of the value of a UAT !