Just wanted to thank you for this solution, I finally put this together today and it's up and running. I've recapped two PLMs but still having reliability issues, mostly the PLM (and therefore the ISY) not seeing devices turn on externally so statuses aren't staying current for programs, etc.
So far so good, although oddly I've had several devices fail after the new setup. Two Icon relay switches, a LampLinc and a six button keypad all will not take the PLM address write. I did finally get one of the Icons going - I had already tried a bunch of things - factory reset it, restored the device, tried to manually write updates, etc. but it would always fail to take the new PLM address. I finally deleted it from ISY, factory reset the Icon, then added it back as a new device and it started working. I'll try to do something similar with the other devices (though one is in the attic - probably not NEC approved).
Like someone else on this thread, about the only X10 thing I care about that I have left is an IR receiver in my home theater, I may see if I can upgrade the ISY with that feature (I need to do something with my Z-Wave module anyway to get above 5.0.14), or find another solution for IR.
Thanks again, and hoping my network is a lot more reliable now!
Gerry