I hear what your saying and I agree as long as you got all that with you and all that. Id think a recipt and the transfer papers for the 14" not shot gun would get you by (although not as safely) as well or at least keep you from staying in jail if they are infact 100% legal. either these are legal or there not, just like any fire arm. Unfortunatly the man not knowing the law can get you busted or at least detained.
With an SBS or AOW you will have a nice official looking document from ATF with all sorts of signatures, tax stamp, etc. on it saying you can legally own it. With a 14 "not a shotgun or AOW" firearm, at most you have a letter from ATF saying it MAY qualify as an illegal AOW depending on how ya carry it. At least with the paperwork ya got proof it's legal.