Funny you should ask...I just finished repairing the spinner on mine. I have two Avistars and the first thing I would recommend is to forget about the one that came with the kit. If you get a chance next time you are near your LHS, get a better one like a Du-Bro or the like. Both of my models ended up shedding the spinner after about the third flight. It appears that if you tighten them too much, the threads split and you lose the spinner. Of course, the inverse is true. Don't tighten them enough and you eventually get the same problem.

I know on my first model, it seemed like the backplate would not fit correctly either. I had to make sure the backplate was snug while I was tightening the prop or it looked to be off a bit. I will try to get my camera working and send a picture of one with just the backplate and prop installed.

T.