In PA you can get into trouble for driving a F250 towing a trailer with a trailer GVW of 10001 lbs or over. That truck trailer combination requires a class A license. However, in the past if you tried to take a test in that combination they would laugh at you and deny the test. It's been challenged recently and a few people have been able to take the test in a similar combination.
Thats the way NH is. If the truck is over 26,000 GVW, commercial is needed, unless its an RV. And its only an RV if it meets certain criteria (has a bed and running water I believe...would have to check). Doesn't matter if its for personal use, it still requires CDL.
They also go by the truck's original data plate. If you take a 5-ton and register it for 25,900 lbs. and you get stopped by the DOT, they check the data plate and you get a ticket regardless of registered weight.
Technically if I hook an M105 trailer behind my Deuce, I need a Class A CDL in NH. The combination of truck and trailer are over 26,000 (2400 lb. trailer, 5000 load capacity=7400 gvw; 13000 lb. Deuce, 10k capacity=24000 gvw, combined for 31,400 GVW.) Just putting a small car trailer behind the Deuce would get me nailed if they bothered to pay attention.
Because every state is different, and even different DOT officers and branches believe different things, your best bet is to go to your local DOT and ask them. Compare what they tell you in person to what you can find for PA official law, then use your judgement for what you have to do to keep everyone happy. Being legal to the technicality of the law doesn't help if the actual DOT officers want to give you a hard time. If you live an area like I do, the actual law means nothing to them.
Example in point, a friend has a M211. It didn't come with turn signals, so according to NH law, none are needed, unless it was factory equipped. Also exempt because he's using antique registration, so he's double exempt. but our local DOT officer told him he better put turn signals on it. He did it, because whether legal or not, this is the officer who he would be dealing with around here. Its easier and cheaper to comply than to go through a court battle with the DOT.
Jim