The true reason the south Florida style grass boats or "sleds" perform in virtually any terrain, when built for the area it is designed to run which is key, the width of the hull is measured by the actual footprint of the hull bottom, not the overall width of the rear gunwhales and the length, they measure from the chines, where the sides are bent, that and minimal taper of the hull, smooth transition rake at the front, proper transom "kickup" and a properly set bottom will allow a well designed boat virtually be on plane in a single hull length with minimal throttle need.
Now compare say a diamondback hull or a reputable glass hull, they are classified as say a 7'wide hull, but this is at rear gunwhale top measurement, if you measure at the chines, nope, you are lucky to have 6'4" of footprint at rear, and the taper of the boat is drastic, so consider how much throttle is needed to get this type of hull onto a plane, and to maintain a plane at low rpm cruise.
Rule of thumb, weight vs horsepower as in anything, it is 70% hull, 30% power for best result, you can have a bad to the bone powerplant and a crappy hull, you will wear out the powerplant having to push the crappy hull, or you can have a moderate engine and a free running and docile hull and not burn up the engine or the fuel for that matter.
Hope this answered the question.