Wow, I didn't know it was still 'top down' weather in Oregon.
Yeah, as the top ages, it shrinks as well. So you can pretty much expect that any 'fix' will be temporary.
Sounds like your fighting a loosing battle, but that doesn't mean it's not worth fighting.
One thing I appreciate about trying to stave off the complete failure of something that's going to have to be replaced eventually, it opens up a special opportunity to try different repairs and see which one comes closest to salvaging it or increases it longevity!
I love feeling the freedom of being able to try new ideas, knowing if I muck it up, it's not a grievous loss.
If you have some old jeans or jean like material in black, I'd try cutting a patch the shape of the damaged area, overlapping by an inch or so. With gloves, work the adhesive into the material on both sides. Then put some adhesive on the damaged and wait for it to skin over a little. Get someone to hold something flat on the other side so you will have a surface to push against and press the patch into place.
You could even let it cure and put another coat of adhesive over it, just not too thick.
If you even remotely question the adhesive, I'd go with some RTV black silicone. I WOULD suggest you do it in a climate controlled area or if you get another *warm-ish* day, so it will cure correctly.
Just some thoughts.
Post back when ya can and let us know how the Kat is doing!
G