I’m putting on a pair of Carbon X’s and the instructions are about as bad as it get’s. Granted, little instruction is needed, but I can’t figure out where the two shimms go. On top or bottom of the aero bars? -KP
Do you mean the crecent “toothed” shims? Or do you mean the round “stack height” shims for the arm rests?

On mine I have two shims on the bar (extensions) one on each extension on the bottom of the extension. So, I have the bull horn bar, the extension, the shim, the bottom clamp - in that order. Nothing between the bullhorn bar and the extensions.
Assuming you are talking about the extension shims, they go between the aluminum side of the clamp and the extensions.