You would think scaling it up would make it slower but in reality just the oposite.
One thing to consider on a Hydro is that your going to get more lift from the hull. The main reason for scaling it up is that at 16 1/2 inches it can't handle the weight of the heavier cells. Plus a modified 05 motor is going to produce more power than a 480. A Brushless would be a real riot.

Trying to put todays batt's and power into that hull as it's designed doesn't work as well as a slightely larger version would.

Ive seen , read and heard of people trying to the same thing only to be dissapointed. The gentleman who designed that boat says the same thing every time " The boat isn't big enough for modern cells and power"

Good Day Mate.
But most important "Have Fun"