It will be a seven stringer. That Hipshot thing looks like a brass (or brass plated) plate with countersunk holes. One of my ideas uses a similar concept.
With respect to torsion, yeah, it could be a problem, but I'm hoping to keep bridge relatively thin/small so there will be a shorter moment arm. Shear forces have me more concerned at the moment (no pun intended).
If the grain is parallel with the strings, it will be stronger for bending/torsion, but has a higher chance of splitting/separating (I found that out when making/using an ebony nut). If the grain is perpendicular to the strings, It won't be as strong, but won't split. I'm going to try perpendicular first, and use four screws in the same spacing as the hipshot bridge. That way, if the ebony doesn't work, I can drill holes for string-thru and use a hipshot.
This may be more fiddly than it's worth, but, eh...it's worth a try.