Also, just as an eye opener, but not to scare you or anything:

Shortly after the start of my take-off roll, I often find myself holding up quite a bit of right rudder, %75 or more of full deflection. Your results may/will vary of course. My left engine is also slower to respond to throttle-ups from idle, than my right engine, and this is the greatest contributor of the yaw-to-left durring take-off on my model.

As an aside, my 40 sized dynaflite p-51 also requred similar amounts of rudder during the take-off run, but this was due to a combination of the already mentioned "p-factor" as well as effects of the helical prop wash hitting top of the fin/rudder on the left side.

-E