jcgalvezv, this comment re the TM751 is intriguing. If I understand correctly, you want to open a TM751, and use the daughterboard along with the Firecracker as an RF link. You're not really intending to use X-10 at all?
I can see why this could work, but why is it desirable? Why not use one of the RX433/TX434 family, or Zigbee or Bluetooth? It's not like X10 component reliability or quality anything to write home about, and I don't think it would be cheaper than '433 family and it certainly wouldn't approach the reliability of the latter, I would think.
I must be missing some advantage - I have several TM751s so if there's a cool use for them I'm overlooking, I'm interested!
-harry