Despite the fact that there are a few folks responding to this thread indicating that they seek the permission of the police, it really lacks wisdom.
1. The police have proven time and time again that they are indeed NOT a well schooled authority on the laws within the state or even the jurisdiction that they serve.
2. The police are NOT on your side, they are in fact on the OPPOSITE side, if they feel any infraction or criminal behavior has taken place, they will clearly define that for you with the "anything you say can and WILL be used AGAINST YOU, they work for and report to the prosecutor, no one else.
3. Police officers are not judges or lawyers and NOTHING they say can they be held accountable for if things go bad later.
4. The theory that this is some type of scale as to how a MWG call may be responded to is inherently flawed as this would indeed be ONE officer's opinion and the odds of that particular officer being the one to respond are almost nil since he/she is answering the phone not working the beat.
5. Even in states where there are no restrictions what so ever there have indeed been misinformed officers go through a variety of harassment methods up to and including drawing and pointing a firearm at a legal citizen.
6. In MO, because of poor choices in the 80's the law is not state wide, many areas have the potential to change the laws weekly, bi-weekly etc. No matter the method used, what applies today, it may not apply within as little as one day.
I would not suggest that an out of state person who holds a CCW practice open carry in MO unless they can afford the legal battle that could become reality and long distance legal battles are not cheap, there would be wisdom in concealing until which time the laws become uniform across the state and you are not at the mercy of some pathetic muni-court trying to retain your freedom.
Do as you wish, I am simply providing the advice and opinion you requested, if you want an accurate answer, contact a bar approved lawyer in the jurisdictions you intend to travel.