The nuts in the firewall should be off toward the left. The plane has right thrust built in, so having the engine sit toward the left is supposed to make the end of the crank line up in the center of the cowl. With the engine on the mount, stretch a string from the center of the stab to the center of the engine thrust washer. Looking down the string should show it to be the center of the fuse.If you set the cowl down on a table nose down, you will see the front of the cowl has the same angle as the firewall. This is common to most aerobatic planes. It has nothing to do with the engine being mounted inverted. The right thrust simply helps offset the thrust of the engine.

David