I have an end broken off a plastic sail panel and have the part broken off still.
Guessing it is ABS like used on E bodys? I used some J-B fast weld way back in 2005 just to get it back on as a temp fix so i ccould have the car in a WOW/ISCA show. And it fell off shortly after, as expected.
I have finaly found the part broken off this week.I had pickled it up so it would not get lost{yea great way to never find it again }So now it is time to fix it right before I lose it again
I have this kit 3-M Automix plastic repair #5883 left over from something else.
Will it work on it or will it just fall off later
If it does not work what else are my options?

Personally I'd plastic weld it, but some epoxies will work as well, just a matter of experimenting.

I would use one of the Plastex products. They work great,
http://plastex.home.att.net/

5883 is made for SMC,FPR and rigid plastics,so you should be fine, but if you know that it's ABS, I'd fire up soldering gun and weld the pieces together first, then rough the repair area and skim it with 5883,sand it down smooth, rough up the backside as well and aplly a good coat on there for better strength,

I picked up a small package of plastic glue at NAPA. It's metacrylate and is a "mix Part A to Part B" type of material. I can't recall tha name right now, but it is in a blister pack with their rear view mirror cement.
Methacrylate is very good as it gets hot, welds the plastic and remains soft (pliable) without getting brittle. If you can't find it, pm me and I'll get the p/n for you.