This is what everyone wants their Icon Remote to do. Transmit RF. And it is a very easy mod if you have a spare UR series remote for parts.
Warning... This will probably void your warranty. A red handled hobby X-Acto knife is a good way to open the remote. Just pry it in the side crack. Don't cut yourself.
The pics pretty much say it all. The E(nable) line is not used. This will make it always transmit RF while it is transmitting IR. This is the same way the new UR74A works. The new UR74A seems to use the same IC-on-board as the new Icon Remote. They use the same codes. The code sheet on the X10 site is wrong for both remotes. The sheet supplied with the new UR74A is correct.
Use code 0999 for X10 RF mode. It generates the proper RF command without any IR carrier. So once connected it works properly. Identical to the UR74A.
Gnd goes to ground of capacitor C2. B+ goes to coil L2 on the side towards IC (black goo) U3. S(ignal) goes to R2 on the side near IC (black goo) U3. And you are done. Mount the board with a couple layers of double sided tape. I also used some hot glue as backup. Mount it 1/8" closer to the batteries then shown in the pictures. This was a little close to a back cabinet mount.
Good Luck.