I do have that part currently, and it is mostly in tact. There are a few small gaps where the plastic has crumbled off but it is probably 95% there. The issue is not around that sealing part but the top flap of the rubber just doesn't seem to be as "sealed" as it was before i did the job.

Do you see any issues with using a small amount of silicone glue to keep the top part from curling up?

Also, can you still source the rubber gasket (even from the dealer or classic center?) Mine is in good shape, but i would also love to have another one as i could replace both of these together in the next year or 2.