I have a Comcast/Motorola box that says RNG200N on the front and DCX3501 on the bottom. I had some trouble downloading the remote so I thought I would share some tips and provide feedback to Sling.
When I went to download the remote, Motorola DCX3501 wasn't available as an option, so I tried Motorola RNG200N. This did not work. I then searched the forums and found a post that suggested using RNG200. Motorola RNG200 did not exist so I tried Comcast RNG200. This did not work. I searched the forums some more and found a post that suggested using Comcast X1. I tried it and it seems to work. The poster said that by using the Comcast X1 remote, some menus/buttons were remained inaccessible since it wasn't the correct remote. I haven't yet found which ones these are.
It would helpful for Sling to provide the correct remote codes for Comcast/Motorola RNG200N.