I succesfully programmed my Radio Shack 15-2104 6-in-1 Universal Remote to control my 5115GHC+. This is much more convenient that having to use 2 remotes.
The answer is called "JP1". If your universal remote has a 6-pin connector in the battery compartment, then you are half way there. Now you need a "JP1" cable. You can make one yourself for about $5 or buy one for about $15. If you don't want to mess with the whole JP1 cable thing, you may get limited functionality by using setup code "0871", though I haven't personally tried this.
All the info and software are located here:
I figured this JP1 stuff out a few years ago as a fun project. Finally one of my trivial pursuits pays dividends!
I'm not affiliated with the above website (other than being a registered member). I just think they do a great job.