The main thing is not to overwritten the holding screws. I do them finger tight only - this does mean you need to keep an eye on them 'cause the buggers will get loose after a long drive.
Morgan actually resprayed the rear panel for me last September and fitted a slightly thicker seal.
I removed the panel a couple of weeks ago, all was well so I waxed the paintwork then cleaned and applied some Vaseline to the seal before replacing.
