The best advice I can give you at this point is to get a JP1 cable. This will let you re-program your OFA remotes from your PC. If you send the 6131 in to be programmed they will substitute it for a JP1-compatible version.

So, if you get a URC-8811 and a JP1 cable, you will be able to use the 6131's learning feature to determine what the codes are for all of the buttons from all of your remotes. You can then use this info to create upgrades which contain codes that even OFA don't know about (as appears to be the case here).

As the whole JP1 process is a user-driven home-made process, you can't buy JP1 cables in the stores and the OFA customer support won't mention it to you either. I can sell you a cable for $15 and I can also sell you a URC-8811 for $19, and shipping for the pair is $4.

If, in the future, you find that you need more URC-6131 remotes, I sell versions of this remote that I have personally modified to be JP1 compatible.