It should be safe to assume there is a template used to create the skins. The top of the seat skin seem tight (in the original post) but the area under the bolsters mentioned seem like there is not enough skin to tuck it under properly. Maybe too much padding was used and therefore did not all of the skin to install perfectly.
It would be nice to know for sure what is going on. Hopefully (jdubs) will followup if he gets it re installed.