Please let us know your results when/if you try with bino viewer.
as for the binoviewer, I can't imagine that assembly would weigh more than my DSLR... I'd hazard a guess you would be just fine with it
I was able to try this quickly tonight and it worked well. I have the Celestron BV (by all accounts identical to the Williams Optics and other entry level BVs) and was able to focus without a barlow in the path. I ended up extending (collapsing?) the tube about half way.
The scope took the weight of the binoviewer without complaint and I was able to use the helical focuser to fine tune the focus as usual.
I'd imagine this big a change in the secondary position has to reduce the effective aperture to some extent but the view of the moon in the binoviewer looked pretty great.