I have a friend that has a Ford PowerStroke and one thing that those guys have found on their trucks is the breather tube/ return line in the fuel tank can be cut shorter. This allows their tanks to increase gallon holding size by about 5-15 gallons. According to my friend the tube that gets cut inside the tank cause a major air pocket for baffling that a Diesel does not have to have. Ford was keeping their cost down by putting the same tanks on the the Gas and Diesel Trucks.
Has anyone check to see if the same thing can be done on the Chevy/GMC Duramax?

The inner sleeve on my 03 does travel down and across the top front of the tank by 6-8 inches. Does this keep you from filling the tank all the way? Would trimming this inner sleeve flush with the tank inlet cause other problems?

It would be nice to have an extra 5 gallons capacity, This would allow you not run the tank down so far but yet have the same range. Or you could could run the tank down with exteneded range.

I will have to look closer the next time I have my tank out.