A Solution with Benefits

It appeared that an external "sight" gauge tube might solve both problems...  A clear tube next to the tank that shows the fuel level and then a crossover line at the bottom that could prevent the fuel from getting stranded.  They are fairly common in industry, but the fittings needed to add one to a plastic gas tank didn't exist yet. 

Once it was realized that the fluid could flow around the outside of the bolt, rather than through the center, it became doable.  Prototypes were made, improvements were made.  We thought we were done and made bigger batches then scrapped those and made more improvements.  Finally the end result is our current product. 

We've been using these systems for over a decade now, in different forms.  The fittings have changed slightly and we've changed the seals from the originals.  They have been completely reliable and leak free (so far).  We changed tanks a few years ago (to change color) and found no problems with the foam either.  We are warned that the lines could harden or get cloudy over time, depending on our gas and oil.  So far our have lasted years, but if you would like new fuel line we'll happily replace it yearly for free.
 

In the past, we used to fill our tanks before every ride.  With gauges, we found that on most rides we would use less than 1/2 a tank of gas.  For us this is for about an hour of cinders riding at 7000'+ elevation.  Now we start rides at 3/4, saving several pounds of high up and badly behaved weight.  For a 15 minute race, starting with 1/2 gallon might be plenty, saving 9 lbs. from a full tank.  A true weight savings was not the goal, but it turned out to be a major benefit.

Another benefit in having the long tube is the ease of draining the tank for before removal or transferring gas to a bike in need out on the trail.