It's probably the resolution from 9ft away, it works fine from a few steps closer.
The move forward/backward movement also gets 'floaty' in tumble from that distance since the size difference in the ball starts getting too small.
Anyway the solution is easy in both cases, just put the sensor bar on the coffee table to play sitting down or set the ps eye to the red setting to zoom in.
The move has one big advantage in that in can keep tracking the pointer when you point off screen. In tumble you can point it all the way around and shine the little laser beam at yourself. That can be useful for quick rotation in fps games. The further you point off-screen the faster your character rotates. Is that used in mag or killzone 3? I found it pretty annoying on the wii that it just tells me I'm not pointing at the screen, yes I know I'm trying to turn around :)
