Update: I painted the mounts and grill. Blog post here. I think the paint holds the grill mesh in a dome shape better than no paint.
The door cards on my ’86 syncro were falling apart down where the previous owner had installed 6″ Boston Acoustics speakers. Really, the entire door card is pretty tired and warped but I chose to just do a quick and dirty reinforcement around the speakers. I used some scrap 1/8″ aluminium sheet to cut out a plate to stiffen the bottom of the card, some 1/2″ plate was turned down to make new bezels for the speakers, and some stainless steel mesh to make new grills.
It turned out more
rugged utilitarian looking than elegant, but much better than before. Oh btw, there are tweeters behind the stock speaker grills up higher on the door. The crossovers are tucked up under the dash.