Found this article regarding double tow. Found it quite interesting. Both minimum age and tow hour restrictions through the Twin Cities metro area.
Recreational Vehicles Combinations. Minnesota allows three-unit RV combinations consisting of a full size pickup truck or recreational trucktractor towing a 5th wheel trailer and one additional trailer that is carrying only a watercraft, motorcycle, motorized bicycle, off-highway motorcycle, snowmobile, all-terrain vehicle, motorized golf cart, or equestrian equipment or supplies, if all the following conditions are met: 1. The combination does not consist of more than three vehicles, and the towing rating of the pickup truck is equal to or greater than the total weight of all vehicles being towed;
2. The combination does not exceed 70 feet in length;
3. The operator of the combination is at least 18 years of age;
4. The trailer carrying a watercraft, motorcycle, motorized bicycle, offhighway motorcycle, snowmobile, all-terrain vehicle, motorized golf cart, or equestrian equipment or supplies meets all requirements of law;
5. The trailers in the combination are connected to the pickup truck and each other in conformity with Minn. Stat. § 169.82; and
6. The combination is not operated within the seven-county metropolitan area, as defined in Minn. Stat. § 473.121 subd. 2, during the hours of 6:00 a.m. to 9:00 a.m. and 4:00 p.m. to 7:00 p.m. on Mondays through Fridays.