All ShockStops come pre-loaded with an average setup of elastomers (60/70 combo) in the +6 degree direction. If you would like to switch the ShockStop to the -6 degree direction, you will need to uninstall the pre-load wedge, take out the elastomers, flip the ShockStop, reinstall the elastomers on the top, and reinstall the pre-load wedge. Remember to do this while the ShockStop is on the bike, adding extra weight to the top of the ShockStop to avoid cross-threading the pre-load wedge. 

We put together a comprehensive instructional video that covers installation and useage topics such as elastomer removal and selection, pre-load wedge installation, removing your old stem, etc. Below are links to each section of the video:

Additionally, here is a picture from the instructions that indicates correct installation of the elastomers: