I think in some applications the loss of aperture for binoviewing is negligible - I'm guessing as I haven't done it yet. Terrestrial spotting would be fine and I'm gonna leap here and say the comfort and efficiency of bino viewing offsets the aperture loss on contrasts on lunar and planetary.
I'm interested in a lot of your results now Mike !
Well, if the effective aperture of the C6 is reduced to 5" with the binoviewer, you still have the equivalent of a 5" binoviewed. That's not so bad. Even so the C6 plus binoviewer will be easier to take out than a 5" refractor. Of course, if I'm binoviewing I'd much rather have a setup where I can use the entire aperture of the C6 - or most of it.
At the end of his tread, Edz appears to concede that this is possible with the C6, but only after much thought and probably more money. I'd rather do the research first before I put out the money. Ideally, I want to binoview with the Burgess binoviewer I already have, and just purchase the adapter and diagonal to make it possible to use most or all of the C6's aperture. I don't want to buy another binoviewer now. If that's not possible, I'll just monoview. No biggie.