Any chance you could post some images of your modifications? I have the backbone system and was going to pick up a Roof Nest sparrow soon. No pressure. Thanks for your time.
Sure thing. After the headache of mounting/dismounting my Roofnest Sparrow on the Rhino Rack, I decided that I would never try that again. Instead, I ended up buying a set of the FrontRunner RTT Quick Disconnect mounts. This system allows me to remove my tent using only 4 buckles, and maintains the functionality of the rack when the tent is not mounted.
These are not meant to work with the Rhino Rack, but I found a way to mount them onto the support crossbars underneath the Pioneer tray by drilling a few holes. To make this work you'd also need to purchase at least one set of rhino rack crossbars, and make a steel L-bracket. I also threw the Roofnest mounting hardware in the trash because the bolts stripped after one use. Recommend not using the supplied-nuts and bolts. Hope this helps!
Here was the final result: