Saw an interesting post on satelliteguys from an installer. He used the reverse band LNB for an install with 16 H25s but three didn't work. He says he found out that it will downgrade itself to 13 tuners depending on what is connected to it. Apparently connecting an HR34 to it will drop it to 13 tuners, as well as a specific model of H25 that he installed one of (he didn't say which one) As far as I've seen, all the tuner chips available range up to 2150 MHz so I wouldn't think it is a problem with some models using tuner chips that have a lower range. Maybe they have some sort of filter inline? Whatever the case, I guess that explains this confusion over whether it supports 13 or 21 tuners. Perhaps it will be possible at some point for someone to compile a list of models that will work with 21 tuners, so those who have more than 13 tuners and want to use a reverse band LNB will know what receivers they need to replace.