I couldn't resist looking up the name of the biggest Missouri Crawdad, its the Longpincer, and its native to the White, which I knew. I don't know how big they get, but I've seen them with bodies close to 5".
If you're worried about losing your traps, drop them right off shore from a landmark in water that is 3' deep according to a pole. Put a large treble, with the points cut off for safety, on the end of the pole. If you put a length of small diameter rope about 5' long, with a weight on the end, and place the trap in an area that you can get in on tight, you can snag it or the rope with your depth pole.
Funnel crawdad traps have a 1 1/2" opening. The ramp type works better though.