The advice to check with the states you plan to go through is the best advice. I can tell you in CA you do in fact need a commercial class 1 with double and tripples. I know because I have the license and pull a utility trailer behind my fifth wheel. I also have read that if your license from your home state allows a certain combo, it may be allowed in a different state, provided that state also allows that type of combo. This means that if you can pull a double trailer and not have a class 1 in your home state, it may be allowed in a state you are visiting, only if they allow doubles also. But you should check first.