Depends on the hull & motor size.
I have a GD 18/44 hull with a 25hp Kohler long tail.
With (2) two hunters, gear, dog & (1) one (70) seventy pound Aquapod, my top speed in shallow water (3 three feet or less) is 18 mph.
My buddy who was running a 16x48 joh-boat hull with a 23 hp MB short tail with the same load was running 20 mph down the same trail.
Due to his hull being lighter, his boat runs faster on the smoother water/airboat trails.
But once we enter the marsh, my hull out performs his due to the smooth bottom, no chines or keel.
When it comes to a MM, everythings a trade off with no perfect boat.
In my opinion, if you want the best performance out of a MM, attach it to a hull that was designed for them.