Since the prices for the 1 cargo cover that will work with the R51 are just too obnoxious for me, I just pieced together something that will work for me. Hit the local fabric/craft supercenter and picked up some sturdy fabric (I felt like a complete tool wandering around the store, and I certainly felt out of place, but the women were almost giddy to help me out). Cut it to size & had the gf's mom sew the seams for me. Picked up some 1/4" elastic cord from the local climbing shop & threaded it through the new cover. I'm still trying to find some better hooks for the ends & there are a few options for those. It may not look pretty, but the only time I've wanted (needed) a cover has been when out & about on travels, with the back end full of stuff. My cover will be able to stretch a lot (I intentionally designed it that way), so I can really pack in the back & the cover will keep it all hidden. Total cost was about $14.
Here's the back w/out cover:
And with the cover (yeah, I know it looks sad just hanging there):
Closeup of one of the corners. As mentioned, I'm still looking for a better hook: