Interesting, I didnt think about that but I guess if the axis are non-planar then you get off axis input as well. It would be interesting to see if this really helps with pitch/roll stability though. I am thinking of it this way: if you could get the heli to hover with less input from the FC by adding dihedral, then I guess it would become less twitchy from the constant corrections given by the FC. I wonder how much lift you lose. If those arms are anything like the F450/550 they flex. So under heavy descents they will inevitably flex upward a lot more than they already are.