The pump collector pot sits on the bottom of the tank and will not allow fuel into it when the level drops below the top, so thats about 3" or 4" of unusable fuel in the bottom of the tank, plenty for cooling. Bunny considered drilling some holes part way down the side of the pot to allow using some more of the fuel in the tank, an idea that has some merit. The only down side of this is that the last few inches of fuel would mean the pump wasn't running fully submerged, this could cause problems maybe?
Most of us don't trust the random fuel contents indications and reset the odometer at every fill up, then do about 200 miles before looking for fuel. I have never had any problem with low fuel using this method. I really don't think any heat build up in the fuel is a problem in the normal installation. I have never found the tank getting hot in use, well not in the UK.
