Derik,
I noticed one thing about your setup....
Your rollers were not folding...
Could you do your setup with folding rollers ?
Would the weight of the rider & bike be enough to keep the rollers from snapping open like a mouse trap !!

Can you still buy non-folding rollers ?
Why did you choose to attach the bungee cord along the top of the roller frame ?
Couldn't you have just drilled a few holes on the sides of the roller frame and used the S hook to attach there ? A couple different holes would allow you to easily fine tune tension of the overall frame ?

Just curious...