Lots of youtube videos on this:
[video=youtube;f32Or4maUug]https://www.youtube.com/watch?v=f32Or4maUug[/video]
In some cases, if you only need 1/2", just sanding off the skin of the foam will allow you to sink deeper into the seat.
[video=youtube;f32Or4maUug]https://www.youtube.com/watch?v=f32Or4maUug[/video]
In some cases, if you only need 1/2", just sanding off the skin of the foam will allow you to sink deeper into the seat.