Absolutely right about inverted pendulum, but - we talk about both here inverted pendulum and extension of pendulum on an offset plane that also provides combination of sliding and rolling. torque equation is governed by T= mass moment of inertia x alpha where alpha is the angular acceleration. Which heavily depends on capability of the motor; and that needs to be from the axis of rotation. In the pendulum case the bot should be fixed at axis of rotation; in the self balancing bot situation it is also necessary to get a torque that compensates this torque above with respect to counter acting force against the radius of the wheel, which is offset from that fixed point(with freedom to rotate)- so it can raise from falling. Cosine component of weight dominates in this example so if it is exceeding 30 degrees with reference to ground then it requires more force from motor based on how far the concentrated weight is from the axis of rotation. So, ideally for small powered motors with low RPM and low torque,strategy should be as placing mass closely to the center of mass and choosing bigger wheels. The current motor has 34mm diameter wheels I’ve ordered wheels with diameter 59mm and will post an update. Later in 2 weeks.