With Hip Wedges you can fit the sides of the seat more snuggly around you.

The positive to this is that it will help you roll, edge and control your kayak in rough conditions.
The disadvantage is that you will reduce your rotation. In some circumstances this is a good trade off...

Note that the hip wedges are designed to fit between your Bumfortable seat (sold separately) and the side of the cockpit - see sketch pic below.