Sounds like a job for 3M Weatherstrip adhesive. Auto parts stores should have it.
I tried that, it didn't last.
How about the type of glue they use for rear view mirrors? An auto parts store may have some.
I think both surfaces have to be pretty flat. The part that the mating flashing is not.
Loctite 406 is specifically formulated for plastic and rubber.
I need something that has fairly quick tack time Taking the entire window down and doing the job on a bench is not very easy. Whatever I do has to be done situ with clamps maybe.
Thanks everyone for taking the time and giving excellent ideas and advice.