Mine are the same. Up to 30 they seem to be good, then after that not so much. And yes, I use them as a means to know what I have starting out. A couple of flights lately, I have needed greater accuracy so I don't land too heavy i.e., fill as much as possible )for next flight) but with 4 people and bags, don't want to land over 3200#. A good fuel stick would give me accuracy to know I had let's say 55 gallons...
I think mine are around 3 gallons low in flight. The attitude of the plane is a little more forward than when on the ground and I suspect that makes up for the difference. The good thing is they show less... if you have lost track of fuel and need them as a safety at least you won't over estimate.
I will make my own from a paint stick or re-score a universal fuel-hawk. I'll do the drain one tank into the other or some method like that and probably 5 gal at a time.
Another question, how do you know you are full? 44.5 gal? I can continue to put more fuel in the tanks if a rock the wings and wait, rock and wait, rinse repeat. From a ferry pilot on here, it has been said that our 89 gal tanks will actually hold 104 gals if we are patient. The tanks are the same size as the 104 gal tanks, but vent at the collar. If that is true (I have not tried to fill 104 gals), then how do you know that you have 44.5 gals in the tanks if you didn't start with an entirely empty tank?