The hose to the caliper exits at a steep angle so I had to run the line along the chainstay. I’d bitch about it more but it works OK for now. This is a 17″ frame and the rear caliper sits pretty close to the seatstay because the rear of the adapter makes it sit up a little bit.
The other issue I am having is that the rotor in the back isn’t big enough to fully hit the entire brake pad in the caliper, but I can’t go any bigger on the rotor because then it hits the inside chainstay.
I actually wanted to go to a smaller rotor, but the caliper isn’t adjustable on the frame. 
RE: Single Speed
If I was building up a single speed from one of these, I’d consider going disc on front and sticking old school V brake on the back. It’d be lighter, both on the bike, and on the wallet. 