I would say they're well worth it, in fact a necessity, if your speed is likely to be very high, say 50 plus a lot of the time, as they make a boat (any boat) travelling at those sort of speeds and above far more 'roll stable', neutral, and generaly more nicely behaved, however, although you don't quote the boat size that will be getting these 115's, I would hazzard a guess your speed will be sub 50 mph most, if not all the time, so I wouldn't waste ya wonga.
All IMHO of course.
PS. they will make manouevering a little easier too, as they mean reverse/forward behaviour will be nice and balanced, especially going astern.
__________________
|