I havent had one flop over yet this year...they are tough!

I think that if you hit them in the vitals they are rarely just going to flop. I shot one this past fall with expandables and hit off target. It just happened to be that off target was right at the base of the neck and he dropped like a fly...

I believe its pretty tough to drop them in their tracks with a fixed blad broadhead and a 300 fps bow, but it will definately kill them just as well.