I have that same plane with an FPE 2.4. I'm sure you know from reading the manual that the fire wall is at zero degrees. I agree with Flypaper except for the 1/8(.125) I think thats alot. My 2.4 has a center to center hole pattern of 3 inches across the top, I'm going to put in 1 1/2 degrees of right thrust. That's .078 thick washer, a little more than half of that 1/8. But even at zero thrust my plane is'nt doing what yours is.