Even with an over-sized engine and or prop, you should be able to get a straight take off roll. Jester_S1 has it right. The first thing you need to do is ensure that the plane will roll straight. A garage floor is a good flat and level place to do this. With the radio on, and the rudder centered, give the plane a gently push. If it won't roll straight for 10 or 20 feet, you need to correct your mains and/or your tail wheel. Second, ensure you have a good +/- 45 deg or so of rudder travel. Then I would try to start the take off roll very slowly and gradually add power only if/when the plane is rolling straight. Yes, the "floor it" method works but only if your left thumb is reasonably skilled, your mains are properly aligned, and you have enough rudder throw to counteract the engine torque. The slow roll is easier to control and to prevent the plane from getting seriously off line. The final piece is fine-tuning the amount of tail wheel authority with the rudder authority. That is, when you get up to speed and the tail wheel lifts, if the rudder and tail wheel are balanced, the plane won't have a tendency to suddenly yaw left or right. Unfortunately, most ARFs have the tail wheel hard-wired to the rudder so its throw is not independently adjustable. If thats the case, your stuck with what you've got unless you're willing to re-engineer the tail wheel set up.