Here we also have what is called bridge law. My understanding is that is not done everywhere. The length of truck and trailer and the number of axles over that distance matters. It matters here because due to length, I cant carry my max capacity on certain combinations of truck and trailer. So there are times (and locations) where regardless of capacity, the overall length can't "bridge" enough to allow you max your truck trailer combination.
All of this, and different interpretations of the law make this really hard when crossing State lines. Some rules are DOT Federal and some are State. Thats why when buying equipment out of State or neighboring States, I hire it. I am not interested in being stuck in BFE red tagged for some jacked up interpretation of the law. There are guys that have that dialed in, and I am not one of them.