My RV a true mileage efficiency challenge

[skyking]

If you are comfortable with heavy fabrication, an aero trailer for your dingy would yield a big gain. Paying another to do it would wipe out any potential savings.
It gets the dingy clear off the ground and takes all the guesswork about flat towing and lubrication of transmissions, transfer cases. It also provides storage for other things.
I have some ideas for the fairing that goes between the trailer and RV, to minimize the gap and resulting turbulent flow in crosswinds.
One downside is finding a place to stow it when you get where you are going. Some places have trailer storage, others not.