No it's not called triple tow as it relates to RVs. It's only called triple towing by those who don't know any better. Many of the RV websites are included in that list of those who don't know any better. Those sites are compiled by people who have no legal training and no knowledge of the law. They interject their opinions.
By legal definition what you are discussing is double tow. That is the way it is defined by Fed DOT and state statutes. If you call any state police or DOT and ask about triple towing they will assume you are talking about pulling 3 trailers which is legal in some states. If you want the correct information you have to learn the correct terminology. Towing 2 trailers in whatever configuration is double towing, not triple towing.
Most states that allow double towing only allow the first to be a 5th wheel. What is allowed for the 2nd trailer varies by state. For example, in IL the only allowed 2nd trailer is boat, ATV, motorcycle or personal watercraft.
You also need to check overall allowed length as it varies greatly by state. Each state sets their own overall length law. One state may grant 70 ft, another 60 ft.
It doesn't matter where you're registered or what your home state allows. You have to comply with the state law in which you are traveling.
"Technically" your truck is not a "tractor". It's a tow vehicle. Thinking your truck a "tractor" and somehow you can then get by under commercial vehicle laws won't fly. You are not acting in a commercial vehicle operation. The laws for RV and commercial vehicles are entirely different. When you are pulling your RV you are not commercial. Forget anything about commercial vehicle laws. They do not apply. Nor do you want to somehow claim you're a commercial vehicle. As a commercial vehicle a LEO does not need any reason to stop you. We can stop you just to conduct a commercial motor vehicle inspection. That means we can go thru your vehicle. No probable cause or reasonable suspicion necessary. It's part of the inspection process. I can assure you that you wouldn't be able to pass a commercial vehicle inspection. Within minutes of starting an inspection you'd have enough violations where you'd be placed out of service and sitting with a pocket full of citations. If you want to claim commercial vehicle then the first thing I'll ask for is a bill of lading. Everything in your trailer better be listed. Also on the bill is where it is being shipped from and to. Not shipping anything anywhere? Then you aren't commercial.
If you want to know what is legal in the states you are traveling then your best bet is to contact the state police/highway patrol in the states you will traveling. When you call here are some tips:
1) Ask for a sworn officer familiar with traffic laws. Many places have non-sworn (non cops) answering the phones. They're dispatchers or call takers. They have no legal training but some think they know the laws and will give answers that are wrong. They act outside the scope of their knowledge and authority. Seems to be a common problem with dispatchers and call takers.
2) Use the correct terminology. If you are pulling 2 trailers then you are double towing. If you say triple towing then the officer will assume you have 3 trailers behind your truck. Also, be sure to clarify that your first towed trailer is a 5th wheel or a straight trailer if that is the case. Laws vary for each.
3) Calling DOT may or may not be the correct office to call depending on the state. For states like IL then DOT is absolutely the wrong place to call. In IL DOT does the road maintenance. They have no authority nor any knowledge of laws. That's not their job. They don't write tickets, we don't fix roads.
4) Who ever you talk to doesn't care what you think the law should be. If you knew the law you wouldn't be calling to ask. I can't tell you the number of times I fielded a call, gave the person the correct legal answer and then they wanted to argue what they thought the law should say. We don't care. Most don't really want to know the correct answer. They just want someone in authority to tell them it's OK to do what they want to do even if it does violate the law. We're not your mother. We don't pat you on the head and tell you it's OK to continue with what you're doing.
5) What ever information you are given no one cares if you agree with it or want to do something else. Again, if a person knew the law then they wouldn't be calling.
6) The most important point - The fat guy wearing a flannel shirt sitting around the campfire is not a legal expert. Most likely he's more full of beer and himself than he is legal knowledge. Just because he spouts off like he thinks he knows the law - he doesn't.
You asked for someone with 1st hand experience. Here's mine. I was in LE 42 years. I was one of 2 of the first LEOs in the state to be certified on motor carrier safety enforcement. I taught truck and traffic law for a number of years. I was recognized by the state courts as an expert witness for truck and traffic laws. I consulted with our state legislature, the Federal Motor Carrier Safety Administration and Fed DOT on truck and traffic laws and enforcement. So I've had more than just a bit of passing experience with truck and traffic laws.
Camped in every state