Many builders complain about the cowling alignment, but they likely do not realize that the engine mount holes are off center to allow right-thrust to be built in. The Left Engine Mount needs to be shimmed with washers. Once that is done, the prop shaft of the engine is right in the middle of the front cowling hole. Forget the right thrust, and you will fight the cowling forever! Photo below shows the washers used.

The cowling does need to be trimmed for the retract servo mount and also around the engine carburetor. A large hole is needed at the bottom of the cowling to access the glow plug as well.