My trailer is 28' with three 5000 lb. axles and plenty of room for my EB inside. I work for an RV manufacturer and we used to build toyhaulers (sold that part of our business to Weekend Warrior a couple years ago). At the time I was looking into trailers I was not confident in the design and construction of typical toyhauler-type trailers to hold up to carrying a heavy load like an EB. Being in the industry I was very familiar with the design of ours (which were pretty good actually, for that market) and most of the toyhauler manufacturers. But even with my employee discount I didn't feel good enough about it to pull the trigger. Even though the toyhauler may have 15,000 lbs of axle capacity, the chassis and box are designed to haul motorcycles and quads, not a 4000 lb. trail-ready 4x4. So I had my trailer built to my specs by a custom trailer manufacturer here in So Cal named Universal Trailers. There is a full build-up thread on it over on the Pirate board, with tons of pictures and updates during the build process. I tow it with an 02 F250 PSD. Fully loaded with the EB, gear, 80 gallons of water, firewood, etc., I'm just under the 20,000 lbs. GCWR of the truck. We've used the hell out of it since we got it and we still love it. I didn't have a lot of the luxuries built into it that many toyhaulers come with these days. Since I spend most of my time outside the trailer when I'm camping, I built it to focus on the basics. It has a full-size shower (VERY important to me) and a shitter with lots of legroom, 80 gallon fresh water, 40/40 black and gray waste tanks, small kitchenette with sink, cooktop and cabinets, and 3-way refrigerator. I have fold-down dinette and sofa that also convert to sleeping bunks or fold up against the wall when I load the EB inside. It is all very comfortable for my wife and I. We have mastiffs and sometimes take them camping with us, and there is plenty of room for them inside. With the EB unloaded its like a huge studio apartment inside. By the way, I didn't need 15,000 lbs capacity. But I wanted 3 axles for extra floatation in some of the desert and beach sandy terrain I go to, and it has proven to be a wise choice. I also had them build it with an extra 4" suspension lift for extra clearance when I get off the pavement. If anybody wants to know more about it check out that thread on Pirate or ask away, I'd be happy to answer any questions.
Dusty