We have done that with some success as well, although not universally. I've found that some cable boxes communicate back to the main office on Ch 116, and applying a channel blocker prevented the boxes from properly picking up guides and so forth. This particular job was in southern Wisconsin.

How about modulating the devices you have on antenna channels? The antenna channels 14-69 do not occupy the same bandwidth as cable channels, so you could do the following:

Send cable through to the cable box/tv location in the clear.
Modulate the channels you need on antenna 50, for example.
Apply a cable box bypass set (Channel Vision, Channel Plus, make your own) to the cable box.
Tune the TV to antenna Ch 4 (cable box), antenna 50 (your stuff)

Any potential problems with this, other than the cable guy undoing your stuff whenever he comes calling?