they do act differently when upside down. they controll the decompression alot better   and slows the tire from droping to fast ( can be bad)  they also can suck air !  when that happens to fix it just turn the shock back over for a while and it will fix its self.. they create air pockets  in the top of the shock insted of breatheing out from the  seal when the shaft goes out.  we have thought we killed 8 rs9000's  but after being off the truck for about a month now we went to warrenty them and they are back to normal !  the air pocket just needed to work its way out.