Thanks for all the possible things to consider. As or the engine, it looks to my eye as if it's 0-0. I think the nut being off-center in the photo is more about camera/lens alignment. But I'll check it out.

The problem with the way I've done the rigging (using fixed 0.6mm music wires) is that they can't be "loosened." They just have to be replaced. And replacing one usually means replacing several.

My main concern was whether the first or the second photo represents the "true reality" for the model. If the first is "true" then there is hugely more dihedral on one side than the other, and the elevator is out of alignment. If the second photo is "true" then the model should only need minor tweaking.