Extended pin boxes do not eliminate the need for a slider hitch on a SB. As the truck turns, and the trailer angle approaches 90 degrees, the pin box is parallel to the cab of the truck. The SB is 21" shorter (6'3") than the long box (8'). On an 8' box, there is more than 4' between the cab and the rear axle (approx location of the 5er pin). 1/2 of an 8' wide trailer is 4', so there is no clearance problem. With the short box, the distance from cab to rear axle is much less than 4', so as the trailer to truck angle approaches 90 degrees, the corner of the camper will hit the cab. The slider hitch fixes this by sliding back about 10" to prvide the necessay clearance.
crebelein: I wasn't trying to talk you out of the SB, just wanted you to know what you need to do to make it work. Lot's of people tow 5ers with SB's.
BTW, the clearance problem is usually only a problem when backing the trailer. Going forward, you usually can't turn sharp enough to get the 5er to hit, although this may be a problem in the '03's since they shortened the box by 3 more inches (all from in front of the axle).
Good luck and enjoy.