Install the engine mount on the firewall, then set the engine in place, just as it will be mounted. Using a long piece of twine or some type of cord that doesn't stretch, hold one end of it on the front of the engine shaft, then move the other end to the tip of the left elevator (as looking from the back of the plane) and mark it where it touches the elevator. Swing the end of the string over to the right elevator tip and the mark should end up slightly further back, if there's right thrust built in.

If there's no right thrust, then add a washer on each of the left engine mount bolts (between the mount and the firewall). That will give you a couple of degrees of right.
Dennis-