I run no rerar on my older banshee. Looks awesome! Heres what I do to make it fit.
1. At the front, where the seat goes up to the gas tank, wrap a bunch of duct tape arount that point of the frame. That keeps the front of the seat in place. Ghetto, I know, but havent experimented with other options.
2. I take plastic tubing. Like for a beer bong. Cut 2 bits of it. Bout 1 1/2 inch long and put into 2 holes at rear of frame where the 2 prongs from the seat fit. that keeps the rear of the seat pretty firm.
3. I just did this: Take lengths of that same hose and slice down the length. Wrap over the subframe where the seat sits. That protects the frame itself and gives more stability.