DH said Bilstein Tech Support (out of Moorseville NC) was terrific. Brian spoke to him for nearly 20min. about the various applications.
The way I understand it is the 5100's are great for lifted or off road trucks that will get a sharp movement, i.e. big pothole. They dampen that type of quick jarring movement. But they don't do anything for the rolling/rocking motion you get with a top heavy truck camper. That's when you should choose the 4600's.
If you are a gear head give them a call b/c the actual interior design/technology of the shocks is different between the two series. And I am not smart enough to get what that is exactly... All I know is that on a stock '06 2500 Dodge Ram CDT 5100's were dangerous with a 1,500lb. TC. DH wouldn't even let me drive it back to the dealer with the TC loaded (25 miles) for the replacement. He's doing it himself at home after work.