[super vw]

Have you thought about the fenders being miss shaped or not the same?
It would be easy for a beetle fender to look right and still be a few Millimeters off from one side to the other.
This could be the case, and if it is. it might just be as easy as bending on of the fenders out or in to make them even (just a little, as you dont want to tweek them) If they are already painted (for the final time) i would not recomend bending the fenders much at all, if any. In doing so it would be easy to crack the paint along the fender lip.

Maybe measure from a fixed point on the body (not fender) out the the fender lip to see if one fender is different. Assuming all the fenders are bolted up tight and not loose.

Later,
Jonathan