In my airplane the gas tanks are rubber bladders and they have a baffle at the inside (low) end to help reduce slosh from the outlet. his keeps the sending unit more stable as well. Maybe the tanks need to have such a feature. But, we never go by the guage in the air anyway--always time.
Maybe Skier;s Chice could sell an aftermarket kit that woul allow us to hook up a 2.5 gallon metal outboard can as a reserve tank????