I started with a very light all aluminum deck over 8.5 wide enclosed. First trip West got into 70 mph winds and felt it trying to blow over. Sold it (person that bought it had it blow over first trip West), and got a 35 foot 8.5 car hauler. Lots of room, very stable, very heavy.
Interior fenders not a big problem. However when getting home from the Togwotee area all the duffel bags and gear would be frozen to the floor. Pulling with a gasser, the size in the wind, and the weight, led me to replace it with a 35 foot all aluminum in line. Using the drive one in, back one in right next to it loading strategy, for the most part lets it haul near the same number of sleds. There are no interior fenders to work around, it is about half the weight, and much easier to pull with my gasser in the wind. It is harder to get around inside when loaded but all gear and duffel bags etc now stay on the sleds and running boards and are not frozen to the floor when we get back to Minnesota. If I never had to pull more than a couple hundred miles, and I had to park and gear up in the trailer, I would consider an 8.5 wide. But for me driving 1000+ miles one way, and having rental accommodations, the 7 foot wide in line all aluminum is where I wish I had started.