I used to use these with a TSU7000 and RFX6000 at one time and I believe that they are indeed the default codeset for Xantech RT-8. IIRC, when you plug in the power to the RT8, you should see the IR receiver light flash a single time, very dim.

Furthermore, with the RFX6000, I had to remove the internal jumper as I had ground loops that caused interference. Once this was done, I was good to go. I was recently running a Xantech CB12 with an RFX9400 with no issues so the RT8 should work just fine with Jumper removed.

Try these codes please. If these do not work, please try adjusting the 'Duration' of the IR code from something other than 'Default'. Start with a large value such as .7s and adjust down until you find something that does not work:

Group On:
900A 006D 0000 0001 16E9 0CF3

Group Off:
900A 006D 0000 0001 16E9 11EE

Output 1:
900A 006D 0000 0001 16E9 01FE

Output 2:
900A 006D 0000 0001 16E9 14EB

Output 3:
900A 006D 0000 0001 16E9 02FD

Output 4:
900A 006D 0000 0001 16E9 03FC

Output 5:
900A 006D 0000 0001 16E9 00FF

Output 6:
900A 006D 0000 0001 16E9 05FA

Output 7:
900A 006D 0000 0001 16E9 06F9

Output 8:
900A 006D 0000 0001 16E9 07F8