I've just scanned this thread, and from what I can gather, the gauge in question reads OK, except at the critical empty end of the scale, so the basic system seems to be working OK. I've had to fit a number of new sender units and gauges on various vehicles, and none of them are exactly precision calibrated instruments. I have dealt with most as follows. Remove sender unit, and drain tank. Next put in a known quantity of fuel, say a gallon. This is, if you like, a "reserve", as it should have this amount available still, when the gauge reads empty. If your gauge was reading too high a level when the tank ran out, bend the float arm slightly upwards. Reinstall and check reading on gauge. If still not showing empty, remove sender and re tweak. Some folk may not agree with this approach, but I can't see any problem, and I've always been happy with my fuel level readings on the road. Why make things complicated, if a simple solution is available? Just my thoughts, for what they are worth.