I only have a Graphire Wacom tablet, but perhaps I can
point you in the right direction. It sounds like you have
"relative" operation on - that is, it works like a mouse, and
if you lift the pen and put it on down elsewhere on the
tablet, the cursor will still be on the place it was when you
lifted. What you want is "absolute" operation - the place
you put the pen equals a place on screen. I set this in the
tooltypes for the driver - don't know where you can
change it though.
If you still have problems to get a "proper circle", it might
be that the pixel ratio (the scale) of your tablet is set
differently to your screen. This too should be controllable
from tooltypes (or some preference-file you might have).
Supposedly the Amiga default settings is not as
streamlined as on the PC.
To be honest, I haven't heard of this tablet being usable on
the Amiga (haven't kept tabs on USB development
though). Do you really have Amiga-specific drivers?
.
SlimJim