Hi Dave,
All I can say is you are sining to the choir. I was moderately familiar with homeplug and most of what you say, just not the specifics of the situation with WiFi etc. There's a lot of bad science and self conflicting things in there, for sure.
One note - yes you can notch, but if you have IM, there'l still be stuff in the notch.
Gud Luk
Steve