I was wondering what your plan was. Seems like this might be difficult to get a decent looking filler piece mated up there though. There will obviously be some kind of seam, much like the goofy (IMHO) looking fender skirt seam on the 89-93 Fleetwood/60 Specials where they meet up with the rear quarter.
Maybe it won't be quite so obvious in this case since it is going to be a straight line more or less. It might almost be less work to just get all the trim from a concours parts car and do it that way. Then again, I think the base deville trim looks better since it is all chrome, I don't like the painted trim on the concours nearly as much.
I'll be looking forward to seeing the pics of this, as it may dictate whether or not I decide to do this mod myself.
BTW Stoney, having seen you modded yours with the lighted C pillar crests, I thought I would point out that I put a lighted crest in my grille along with a Cadillac script from a 1990 grille, looks good but mounting it was a job. I had to get my sheetmetal guy to supply me some aluminum that I fabricated into special brackets that retain the crest/wreath/script from the rear of the grille. I will try to get some pics up here sometime.
Also I have to say, I'm surprised you took the hole saw to your sail panels [though the results are good!], I had thought about doing this but didn't have the stomach to cut into my baby like that, especially since those lighted crests will burn out eventually and won't be available for replacement as they are already in short supply.