Okay, here's the deal. Sit down and let's put the end cap on this, IMO
Two identical boats.... one half loaded with fuel and water .... same weather and water conditions, same RPMs, clean bottom. The other boat, a full time cruiser or live aboard. Which one will get the best mileage?
Next take the same identical boats, move the load from boat B to boat A. One might expect the mileage to be identical but, on just the reverse boat.
I maintain, it wont happen. It may be close but not, identical. WHY? Daymned if I know why but, it just wont be.
Comparing a displacement hull to a semi-displacement boat.... the old apple and oranges comparison.
Watch your fuel usage meter/gauge ..... what is best for you, is best for you.
IF you are burning 2gph at a given speed. We know it will take X time to get to our destination. Compare that to a semi-displacement hull that burns Y+ gph a speed+, sure you get to your destination but, at what fuel cost.
If you are racing the weather and or tide through the cut, you lose interest in fuel economy, that too is a given.
Basically, the only way you can increase your own fuel economy is to start throwing the stuff overboard. That's not really economical because you will need to replace it. LOL
You bought the boat, you were given the headaches along with the boat. There is very little you can physically do to improve fuel economy other than determine your very own "sweet spot" as determined by that magical gph read out.
Those are my thoughts on the fuel economy.