I run 2 48's and a 66 which was the biggest you could get at the time. Boat about the same size as yours. The 66 on a bridle does pretty good on not to bad days. Other times I have to add the other 2 to get down where I need to be. If they had of had the 77 when I bought mine that's what I would have had. Like Yikes said if only one get the 77. You can kinda control your speed by pulling closer or letting out a little more rope. 2 makes boat control a lot easier. Just my opinion but don't think you can go to big.
http://www.cabelas.com/product/Cabel...h-All+Products
These are the best in my opinion. Have to watch them, the sometimes put them on some really good sales. I started with one of those Vinale socks and hated it.