While one may argue the Constitutionality of a law all day long, unless you want to go to Court, I'd quit carry of anything over 3.5".
5-73-120,121; travelling exception; sec. 120 bans carry of anything with intent to use as a weapon. A three-justice dissent in Garcia v State 969 S.W.2d 591 (1998) makes a good argument against the constitutionality of the 3.5" limit, with a good U.S. Supreme Court quote toward the end of the dissent. Sec. 120 was enacted after 121, and they overlap; 121 probably should have been repealed, and 121 is probably unconstitutional. Also, Nesdahl v State 890 S.W.2d 596 (1995) and Smith v State 411 S.W.2d 510 (1967).