Thats one of the best fitting on the net in a Buick that I have seen, raise the rear part a little behind the rear side window and make it a swing out with the right fittings and for fit and everyday "usability" I would say it doesn't get any better.
PS: most of the welds look good but a few of the hard to get to ones could be improved along with some areas on the sealing plates but overall a good job!