Aircraft MFG should provide the degree off right thrust needed set eng. Normal setting on most will be about 2.5 degrees of right thrust. As someone stated the engine must be moved off center line to mate the spinner to the cowl. Thrust on the up/down should be 0 degrees. I lways find it very helpful to have a digital level ( Sears has a 10 in, digital that will give you a reading withen 1/10 of a degree. these are about $35. I also use this to check wing and stab incidence. ) Just because it an ARF, doesn't mean it is right.