Since you're running with a trike configuration, I agree that it's probably a "toe-out" problem, and p-factor shouldn't come into play.

Here's a little trick I used back when I first learned take-offs.

Remove the wing, and put a plastic bag over the wing saddle instead (only 2-4 elastics needed). This way you can practice high speed handling without fear of the plane taking off. It may look stupid, but not as stupid as crashing when you took off by accident, and weren't ready. This will also maintain pressure on the wheels during higher speed (takeoff speed), in case the weaving is due to the wings lifting the wheels a smidge.

Good luck, and keep practicing...