Kelly is right on with the Knubster
Picked up the Knubster for my Rich Price and let me tell you, that thing is freakin awesome. It really does what it says as I had a great chance to put it to the test yesterday through 2 tides, barreling beach break head + and screaming. It really does increase drive without the drag of a tri, although when I look at my fin set up, I'm like holy crap there is a lot of **** there. I have to say that I think its the best of both worlds. With the Knubster the board didnt get too loose off the top like a quad sometimes will and it takes the drift out of the board, the 2 worst traits of a quad in my opinion. I think I might also grovel with just the front fins in and the Knubster, the possibilities are multiplied with this thing. I was given it as a gift from a shaper friend and if you own a 5 box set up, get one.