In my Partners, I'm running an R921 (essentially the same receiver as the AR9000) and have two satellites. One has the standard six inch remote extension, and the other has a 36 inch remote extension. Oddly enough, the remote on the 36 inch extension is the one outside of carbon fiber completely and has the weakest reception (if you call 25 frame losses weak, the other receivers reported back 9 frame losses each). You really don't need two remote antennas, the one that comes with the receiver is plenty sufficient.

Actually I looked at the weight specs for the receivers, go with the AR9000, it's one gram heavier than the AR7000. Go with the nine channel.

Problem solved.