Why do some of the poses on my Lulu cuffs sink below the ground or float above the ground?

The "height" of the animations in SL are determined by the avie's height.

If you play an avie who is much shorter than normal, you might find that in certain poses, you will sink a bit into the ground. This is more apparent with certain poses in the PLUS cuffs than the Signature Cuffs.

Conversely if you are a lot taller than average, you might float a bit higher in the air.

This is pretty much an SL limitation.

But some viewers allow you to adjust your "float height", or avatar offset.

Phoenix (a very popular viewer): On the viewer menu at the top, go to Edit > Preferences > Phoenix > Avatar and adjust the Z Modifier.

RLV v2 also has a bounding box adjustment at the top of the viewer.

(If you know any other viewers that can do this, please IM Lulu Ludovico or send a note).