The first tip is to check the seat edge springs, if applicable. As expected, ours were broken. The answer to this was to install a block of high-density foam under the outer corners of the seat. Spray adhesive should be used to help keep the foam in place. Later-model seats don’t always have this side spring and won’t need the added foam. If you don’t have any high-density foam, you can cut a piece of foam from your old base foam and use it. It’s not as dense, but it’s free.