I have an '05 I bought used with exactly the situation that Motor31 describes.
Replaced the 16" wheels/tires with 17.5" wheels and Michelin XTAs LR J that I got from
www.trailertiresandwheels.com and have been completely satisfied with the changeout. 5 seasons of travel on them, very little wear and no flats. The XTAs eacn have a capacity of 4805 lbs, giving me a lot of weight room on my unit.
Its a simple swap, just takes about $2000 to do it.
Joe