What?? Seriously - unless you've actually got a clue what you're talking about, then don't post!!
OK - back on topic. I went from a 7'6" popout (riding slop) to a 9'2" custom (graduated onto clean waves) and then had a play with a 6'10" Magic Carpet.
When I went from popout to longboard, I found myself pearling, as I was too used to being up near the front to get the speed up.
When I first used the Carpet, I was lying too near the back and not paddling hard enough, as I was used to the longer board.
I also found the carpet to be more unstable laterally, making pop-ups a lot slower, meaning I missed the wave. This was especially true in the white water or on choppy days. I felt like a total kook all over again until I'd had quite a few sessions on the board, getting used to where to lie on it to paddle, how it picked up the wave, etc
Now - I'm no expert, but if you're still in the whitewater, I'd try getting into the 'smoother' clean waves to see if that helps with stability. I'd also get into the habit of paddling just a couple of strokes more than you used to on the old board and maybe shifting an inch or so forward to stop the board stalling as you paddle.
But, as with most things, it's just a case of getting used to something new and practising...........
