On I-64 today just outside St. Louis, and was passed by a fairly big fiver. It was a Mountain-air and I'm guessing perhaps 30-35 ft, What was interesting was that the trailer was quite high off the ...
I have a 2008 Newmar Kountry Aire 5th wheel that has dual wheels on each of its 2 axles. It is just under 40' long, with a gross weight limit of about 20,000#, although the last time I weighed it, we were around 18,500# as I recall.