As an aside on the practicalities of checking fuel, in the R22 the CAA have MANDATED that a secondary method of fuel checking is available, other than the gauges.
For those who don't know, the R22 has one main fuel tank, on the left hand side just below the pylon. There is sometimes an optional aux tank on the right hand side, smaller in capacity. All up about 3 hours worth of fuel. You can see to the bottom of both tanks but there are no markings on the tank to provide any calibration to the naked eye.
There is also a low fuel light which gives about 5 minutes warning of fuel exhaustion.
Anyway - back to the point. The secondary aid is a calibrated piece of metal which is dipped into the tanks. It works well, and if you correlate with the gauges and the amount uplifted you should be OK. It seems that the Seneca, and lots of other types, don't have the ability to even do this, so why aren't we tackling the problem at source rather than blaming a pilot for running out of fuel when there's no easy, simple way to measure fuel contents at source ?
P.S. I preferred the wooden broomstick with marking on it that we used at Bankstown when I was learning to subdue helicopters - it stayed wet for a time after you took it out, and the markings were accurate !