[Not2B]

You might be surprised - it could be easier to balance with the weight at the top of the pendulum.

You can go through the physics - OR - and this will help visualize it...

Go get a broom or a stick with one heavy end and one light end. Try balancing it on your hand with the heavy end on the low side. Now try it with the heavy end on the high side. Which was easier? Why?

NOW - if you do the physics, you have something to compare it to so you don't get confused. I admit, at first it seems like it would be better to have the weight low... but momentum is a powerful thing...

Good luck!

P.S.- I know this is the easy way out, but you could mount a range finder on either side - if the device starts to tip (on flat land) the distances will be different, and you can straighten out. Just hope no one walks into the field the ranger finder - because you'll end up on the floor. And don't get close to a wall. And stay off hills. And clutter on the ground. And.. and.. and..