Greg,
I know what doesn't on my 2002 sportsman...just by a 1/2 or so in width (front to back). I bought an 18 x18 x 30 frigid rigid after measuring but didn't account for the outside hinge depth. The cooler slides under the seat and is not too tall but will not open but a short distance due to top hitting the cross rail. I presently have an igloo 72 under there and it fits fine. If you know anyone looking for a good deal on a frigid rigid, sent them my way. Good luck.