I installed a set of Bilstein F4-BE5-A935-H0 on my 2005 FX4, and I'm not sure if I put them on correctly. There was no installation instructions, and I wasn't clear on which way the piston should go up or down? The way I have them installed is with the piston on the top, but the Bilstein stickers are upside down.
Here is a pic of them installed:

 

there was much debate about this in the 04+ section. at anyrate, someone ended up calling Bilstein about the matter. They said that the shock should be mounted so you can read "Bilstein", so you have yours upside down. another member said another added benefit is that you reduce unsprung weight when you mount them correctly, though i doubt you'd ever be able to tell any difference.

BTW, i put 5100's on mine. getting them into the shock perch was fun wasn't it?

 

Took mine in to get installed and they ended up it upside down. I should've mentioned how they were suppose to be mounted. At least in was free to make a long story short. Rides better but I'll have it reversed later.

 

Big Stick is correct!
I called Bilstein before i installed my 5100 and they said you should be able to read there name when installed. That puts the rubber boot in the down position.