My boards don't move. I would think you could use some Velcro to hold it in place.
As for the cushions my wife placed some rubber mats that you would place under a rug to hold it in place, under the cushions. They look like rubber netting. You can get them at Wal-Mart, Lowe's, etc...
Russ & Kim
2014 Alpine 3600RS
2007 Dodge Ram 3500 5.9 4X4
2008 Harley Davidson Road King 105th Anniversary
(2011-5 bad year)(2012-40)(2013-45)(2014-23)