The mod that OkieGringo posted in that thread is to fill the regular diesel tanks fuller / faster. Basically it eliminates the expansion space a the top of the tank that is there for gasoline, which has a much higher rate of expansion. When I was a trucker, we filled the side tanks until they were filled to the brim. Of course, if you didn't drive the truck and use some fuel, there was some risk of overflowing if the fuel heated up.