I would advise against running a dslr. They are heavy which isn't good on your eyepiece.your eyepiece might loosen up on you. Ask me how I know..... They are also harder to figure out behind a spotter.
I used the Vortex adapter for my Razor HD w/ a Canon Rebel XT, and it worked suitably, but I much prefer my Nikon J1 for digiscoping. A mirrorless SLR can autofocus using contrast detection, which works well for digiscoping.
If you could get the Swarovski UCA to work with the Razor, it might make using your D5100 much more effective.
I have a Canon DSLR and a Razor 85 and it works well but is cumbersome compaired to a point and shoot. I use a 50mm lens and just screw the Vortex adapter to the filter threads. My 50mm is an older model and all metal construction. Not sure how the newer plastic ones would hold up. I also use a longer mounting plate to attach to the tripod to help balance the extra weight of the camera on the back of the scope. It seems that video always turns out better than pictures if there is much distance involved. If the weather is decent this weekend I might make it out to test both setups.
I made some homemade adapters from PVC fittings and velcro that work great. Even made one for my phone. They slide over the eye piece similar to the Tines up. The same size works on my friends Swarovski too.