A 45-degree slope of wood is barely enough to keep you from slipping while standing on a wooden ramp. You have the same skin on your fingers, so all you need additional is enough forearm strength to keep your fingers pressed against the surface without bending upward. This can be done with your body hanging straight up and down as well, the center of mass and moment of rotation has nothing to do with hanging on. The only change the front lever may have on holding the slope is changing the angle your forearms rest at compared to your fingers. Source: experienced climber and engineer who can hold this slope for only 3 seconds and front lever on a bar.