well frank since you live in florida and see lots of boats heres another analogy.
a 22' boat with a single outboard might go say 40 mph. add a second motor and you might gain another 5 mph.
how many boats are you seeing here with 3 motors and some with 4?
how come none, spelled none of the serious off shore and tournament fisherman are using 20 footers with one engine?
no doubt for what you do the guns you use fit the bill very nicely. there would be no reason for you to need a 7 mag.
ive owned several 7 mags but no longer own one. they simply arent enough gun for what i enjoy doing.
there comes a point where size and cost are secondary to what your goals are.
if it takes 4 big engines to get there so be it.
were either going or were not.
that coming from a guy with a 17 footer with a single 90 by the way.