The window rubber seals were no good for me--too cramped and wouldn't allow the frame itself to close around the glass. To fix it, I used black silicone as both sealant and cushion.
Holding the frame in tight while the silicone sets.The upper frame is massive pain in the ass. Really frustrating. Hard to get into the main frame, a bit thin in spots, and the L-brackets on the ends are shot/rotted/dead.
This one is fine.
But the end of the frame is buggered.
Here's some scrap to replace the rusted one.
Black silicone into the upper frame.
Installed. I'm not loving it.