I travel 120 miles round trip on I-65 5 days a week going to and from work. The last third of my drive each AM has a VERY strong DOT presence. I have seen a few people pass the AL DOT officers while tandem towing and have not ever witnessed the 'perpetrators' getting pulled over or fined.
With that said, If I tried it for 1 mile, they would put me under the jail. LOL
The AL DOT 'seems' to target large scale trucking companies or the opposite end of the scale and target farmers that only get a 18 wheeler out a couple of times per year.
Oaklevel makes a great point, if something were to happen, your insurance company is going to laugh at you which is reason alone enough to not do it IMO.