Adding AM21s

I just got a call from a home theater integrator that is also a residential DirecTV dealer, but they lost their key DirecTV expert a few months ago and don't have the in-house DirecTV knowledge that they once had and, hopefully, will eventually regain.

Anyway, they have a home theater customer whose system they maintain in a condo that I have outfitted with dual stacked Ku trunklines for Sats A B and C. In this application, we have two home runs to the unit's telecommunication distribution point, we then use two Sonora 575D destackers and feed their outputs into an Eagle/Aspen 5x4 switch to support two old dual input HD TIVOs. I forget their model number.

The building also has a doozie of an off-air master antenna system that I built, which pulls in 18 broadcast HDTV stations from six cities (Washington and Baltimore DMAs), so the HD TIVOs tune those as well as the nine DirecTV Ku HDTV channels.

Apparently, DirecTV called this customer, perhaps not realizing he had a community antenna and no access to Ka signals, and came to his condo to istall the new HR21s. While they get all the Kuu channels, they do not have broadcast tuners in them.

We will eventually be working out an SWM solution for this customer's Ka needs, but even when that is in place, DirecTV offers less than half as many broadcast HDTV locals as he can get off his building's antenna system, so he will have to add at least one broadcast HDTV tuner, and probably broadcast HDTV recording capability.

Is it as simple as piggybacking an AM21 onto each HR21, or is there more to it than that? Will the HR21 record the broadcast HDTV? Will the system integrator have to establish an AN21-to-HDMI output path, or will the broadcast HDTV output use the same output path as the HR21 it will be connected to? Do an AM21 and an HR21 together have the same functionallity as a single, integrated unit would, or will there be some combinations of recording, watching, pausing and switching that he can do now with his TIVO HDTV that he might not be able to do with this newer hardware?

He has a Crestron remote control system. Are there additional AM21 commands that will have to be programmed into it?