We have seen several 48 foot 5th wheel campers, and other than fewer available camping sites due to length, they look fine. All the ones we've seen were pulled by highway road tractors, and all were over length for many states. Overall I don't see any issues as long as you have a good tow vehicle and willing to risk the length. Round numbers we are 63 feet, and 83 feet in Wyoming double towing with our tractor with a 36 foot 5th wheel, and sometimes a 16 foot flat or enclosed 2nd trailer (+4 for the tongue) . I prefer to be able to get to a legal length if required. For some reference, we're about 44000 lbs with two pieces, and with an almost antique 3406b Caterpillar engine set at a measly (by today's standards) 400 hp, 15spd trans, we can pull the I70 Eisenhower tunnel grades at 50 mph. I say get what you want.
