My DR400 had three tanks, two in the wings giving just over an hour each, and one large one in the fuselage. The gage in the fuselage tank was very good, and the low level warning light was also spot on, but with 2 hours visually checked fuel in the wings it never caused me a concern. The fuel pressure waning light will allow you to run the rear tank to empty without the donkey missing. This also gives a known level to fill up from which allows a good check on the gauge.
Rod1