Last night I noticed a problem with the setup using a third receiver for just C band in the bedroom.
I had the living room TV on a Ku satellite and was planning to watch a show in half an hour on C band. On a trip to the bedroom, decided to go ahead and move the C band dish to the satellite I'd be watching in half an hour. When I did, the signal on Ku in the living room started freezing. Moved the C band dish back and the living room unit runs right again.
My speculation is the third receiver does the user a "favor" and when signal is lost; starts looking for it by trying different diseqc switch settings until a signal is found, and this signal was getting coupled to the living room diseqc switch, changing it, and freezing the picture.
So this morning took one of the 2x4 multiswitches and inserted it in place of a barrel connector in the C band coax direct to the bedroom receiver. My previous experiments with the multiswitch showed nearly no 22KHz signal coupled through the 2x4 switch.
Well that seems to have cured the lost of signal condition interference I was getting.