Forum

I have limited experience with PtP wireless links but know some of the theory. What I'm am looking for is advice on best practices. I will devour the CWDP book when it comes out but until then I need advice from the smart money on the forums. Here is the scenario:
I have a neighbor that has a 5 story building, I will call building A, that wants to setup about a 14 mile backup wireless circuit to another office, I will call this building C. They have two problems 1) their 5 story building isn't tall enough to make the link 2) the 19 story building, that I will call building B, in their LOS. They have contracted a wireless company to make a design for them. So their design is as follows:
They would like to repeat the signal of off the top of building B. Building A will have a panel antenna, not specs yet, and a matching one on building B. Building A is approximately 800' from building B. Building B will then retransmit the signal via a 33.5 dBi parabolic dish to office C. I know panel antenna can have a fairly wide elevation. They will be co-locating the two radios on building B by configuring the radio out of phase. The radios will be configured for 5.725-5.825GHz. I'm not a real big fan of losing my entire UNII-3 band as I try not to use UNII-2 because of the roaming concerns possible. I am thinking of suggesting that they use dish between A and B and turn the power down. Anyone ever do something like this? I would like have an alternate option for my customer, when I let them know what they are about to use. If it is pertinent, you may want to know that the radio system is a Proxim GX-90.