Modifying Rear Fenders

A couple months ago I took off the stupid looking stock flares and trimmed my fenders, in preparation for a lift that I'll eventually get around to, and now I think it would look better if the wheel well openings in the rear were symmetrical with the fronts. I was thinking I could just trim further up and reweld in some sheet metal to fill the gap, but would that be too high to be possible, or interfere with the wells on the interior of the XJ?

Just dont want to start to do this and end up having to re-fabricate everything behind the rear fenders.

Thanks,
Jeff