Tikkamike:
I'm not saying that your law enforcement friend didn't give you good info, but I would suggest that you contact someone that deals with commercial vehicle rules for your state. Commercial Vehicle Officers (CVO's) have specialized training and hands on experience with towing and towing requirements.
They have CVO's in most states because the rules are complex and difficult to decipher just by reading the statutes.
Also, there are no reciprocity agreements between states regarding towing as far as I know. That means that just because you're legal in your home state, you might not be legal in another state.
Someone that can double tow in Montana, can't double tow in Washington.