As I said in a related post, mercury switches would help get you to true horizontal - I can imagine a system that is switchable between "true horizontal level" and "tractor wheelbase horizontal".
Neither is difficult, BOTH would be a "nice to have".
Salvage some old circular room thermostats, probably need two of them, adjust their difference for how "precise" you want to feel the need.
Neither is difficult, BOTH would be a "nice to have".
Salvage some old circular room thermostats, probably need two of them, adjust their difference for how "precise" you want to feel the need.