I don't think I have ever seen diminsional rules as far as the size and shape of the box. Most orginizations rules state no farther forward than 60" from the center of the front axle to the farthest point of the weight balast, wether it be the weights themselves, the bracket, or the whole entire box. Basically which ever part sticks out the farthest. Probably the only thing that can stick out farther than that would be a tow hook for when your truck breaks and can be pulled off the track faster rather than having to crawl under the truck to find a place to hook to or wrapping a chain around the weight bracket/box its self.