The calculator in FH's link already takes all that into account. It looks at the loads on the surface and the angular deflection and then you enter the servo angular travel (+ and - 45 by default) and it tells you what the load is ON THE SERVO. So if it says 14 in-oz then you need at least a 16 in-oz servo. The assumption being that the servo will stall at 16 in-oz so you need some overhead.

The only thing the calculator does not take into consideration from what I can see is any friction in the system. So if you use tube in tube or wire in tube pushrods or if the clevis pins are a tight force fit in some of the holes then the need for more servo power will be there. You can test some of that friction by using a scale and pulling against the friction.

If you're trying to educate the guys I'd just do the calcs and print the screens.