That is a good one, I never really thought about using a "Skin Effect" to send IR data on a DSS feed cable with diplexers as well. But it does sound like it could be trouble. But if you are planning on using diplexers to combine and then split apart the signals you may have trouble also adding an injector in line on top of all that. Could you just send it over power line or wireless? I know that sounds kinda amaturish but if it's all ya got?!?