I ride in Missouri all the time. I have "seen" lots of realy tall Apes. I don't know where they measure from during inspection but over here by St. Louis they don't seem to enforce it on the street.

 

that law and many others are up to each LEO to define as they see fit. hopefully they all agreewith each other. but I believe that if youtake a level and put it on top of your bars make it level (get two more hands) and have them measure from the seat to the level. that will be your measurment and you can tell anyone that asks exactly what height you are running.
I think that most LEOs will not bother you if your bars are below your shoulders. unless you have a 10 up frame. I think you'll find that even the stock bars on most bikes are going to be around 15 or more inches above the seat. that's why the laws suck that tell you from the seat. Here in Washington you can be 30 inches above the seat! I think that you'll find that 20 inch apes will fit this law.

 

In our part of the state, the cops are too busy trying to get the REAL bad guys, they don't even mess with bikes, and that's a compliment to the cops!!!