>>Although there isn't a way to visualize in Moi which side is the positive normal side

Not directly but....

This trick works only with single surface, not joined, so you need to copy a one single surface from your joined object. (if you have joined object)

Click command >CPlane< and move the crosshairs along the "edge" and see what happens and cancel command..... File attached....

Other command that use normal's is>Shell< but notice, again single surface.

First method is easy....

Thanks for ....