I don't know that you will be able to find the Minnesota statute or regulation on point. If you can, I will be grateful for sure but my search led me to a more general question.
MN has a comparatively easy to use online statute library. https://www.revisor.leg.state.mn.us/ I searched there for trailer and could not find any regulation about how far off the back of a trailer a load can hang (or how far a load can hang off the back of a trailer). I searched CA's statutes and found their rule:
Vehicle Code - VEH
DIVISION 15. CHAPTER 4. Length [35400 - 35414]
The load upon any motor vehicle alone or an independent load only upon a trailer or semitrailer shall not extend to the rear beyond the last point of support for a greater distance than that equal to two-thirds of the length of the wheelbase of the vehicle carrying such load, except that the wheelbase of a semitrailer shall be considered as the distance between the rearmost axle of the towing vehicle and the rearmost axle of the semitrailer.
So I know that some states regulate this stuff.
The fact that I cannot find a statute in MN leads me to hesitantly conclude that the statute does not exist. However, if I get pulled over and cited I will not be surprised that the rule exists and that I just missed it.
So, with something like this, how does one go about exhausting the search and (perhaps more interestingly) can we use as a defense the extent to which we searched and the extent to which the statute was nearly impossible to find?
Oh - and is there a rule in MN about load-overhang?