My two cents on the Louvre subject...more preventive than corrective. I bought my D back in '88 and it had a minor crack where the left side gas strut connected to the louvre. When new, the struts presented considerable closure resistance and made a fulcrum effect that was just begging a crack. In my opinion, the struts were too short-- should have been atached to the louvre closer to the rear end of the car.
My fix was to fashion two aluminum strips to reinforce the inside of the left and right louvre rails, and to replace the short struts with long struts similar to those used to support the front hood.
1: Make a masking tape pattern of the left and right inside louvre support rails.
2: Carefully remove the tape pattern and apply it to a strip of aluminum purchased from the home-utility metal rack at Home Depot or similar store.
3: Cut the aluminum to match the pattern. I used a metal nibbling tool, used to find 'em at Radio Shack; don't know if they still sell them.
4: Select two suitable long struts. I used the spent struts from an '81 Datsun 200SX hatchback; they wouldn't hold up the heavy hatch door, but they held (and still hold) the DMC louvres just fine. If you use new ones, look up the 200SX cross reference so you will get struts with the right end size and thin enough to clear the DMC side panels.
5: Remove the original struts
6: Remove the strut mounting brackets from the louvre
7: Mount the brackets to the slidebar end of the new struts
8: Mount the strut casings to the car
9: With the struts fully extended, raise and hold open the louvres and position the original mounting bracket where it meets the louvre rail(s)
10: Use a pencil to mark the louvre rails where the bracket mounting holes will be.
11 (This is a little difficult) One at a time, compress a strut, close the louvre, and make sure the louvre will close fully with the bracket position you chose. If the strut is too long, you may find that it won't fully close ( i.e., the bracket holes can't be made to line up with your pencil marks). This is easy if you use old Datsun struts, might be difficult to manually compress if you use new ones.
12: If all is OK, drill and countersink two mounting holes in each side of the louvre exactly like the originals.
13: Temporarly attach the struts and make sure the louvres open and close OK
14: Remove the strut mounting brackets and prop up the louvre
15: Hold the aluminum strip in place and mark the original strut mounting holes and the new holes.
16: Find four screws (two per side)and nuts that match as close as possible the original mounting screws
17: Mark and drill the aluminum strips
18: Reattach the strut bracket and the aluminum using the original screws and nuts.
19: Put the new screws through the original strut mounting holes in the louvre and through the aluminum strip.
20: You may want to drill and countersink more holes along the length of the louvre.
21: Mask off the louvre and paint the strip and screwheads with Krylon Semi-Flat Black acrylic spray paint (great match for the original finish.
Note: I have no idea whether this will affect whether luggage racks will still fit.