Hey scotty, I put the knubster it the top tab, meaning the the one closer to the nose of the board, which does put it right in the middle of the back quad fins, if you put it in the rear tab closest to the tail, it anchors the board and makes it next to impossible to turn, which is what happened to me the first time i tried it, the next day, just thought i put it in the top tab and it went magic.
Because of the stealth's unique wide bat tail, and the relation of the rear quad fins to the bat points in the tail, the board pivots on a dime, in smaller or fuller waves, the stealth performs as a quad with no problems, its when you start getting into 4-6 solid waves you will notice the board will weave more than needed giving you that skatey feel, and this is where the knubster comes into play. Positioned in the top tab the knubster just straightens your down the line drive and gives that extra needed hold when hard bottom turning. Best of all there is 0 impact on the release when cracking it off the top of a wave.
Actually in the picture of me a few post up, I didn't have the knubster then just the quad setup, and out of the six shots you see, it was the first image where I'm doing a hard bottom turn where I felt the most out of control, like the board was about to pivot from underfoot, and I remember i had to hold to turn and hit the section a little further down than i actually wanted too. That's the difference the knubster has made with this board, gives you that thruster control feeling but with all the speed the quad.
hope this helps scotty,
If in doubt give it go yourself, you'll start felling it work after a few waves, and once you do the knubster wont come out again.