Forester, I think your math is right. I just bought four sticks, and practiced quite a bit with them, and agree with what you came up with.
as mentioned, above, we often feel higher than we really are. I brought a tape measure with me, and the base of my stand was aprox 18', and I would have sworn I was over 20'.
(you are right, that the 4th stick becomes your step/handle to safely get on your stand)
As for the sticks, when I mounted my first one, and stepped on it, I thought "no way this is going to work", but they work great, don't budge or wiggle, and act like they become part of the tree. I'm really impressed. In fact, it's like they are glued to the tree.
Like others, I'm stretching them out to get a bit more height also. I never used screw-in steps, but I am really pleased with my Lone Wolf hang on stand, combined with the steps. Quality product, for sure.
Good luck.