Rubber Bed mats?

You need a thin rubber mat to prevent shifting and sliding. Even with a spray in liner, it is too slick to keep your TC in place. If your truck cab or rails are too tall for your TC, thicker horse stall mats will build up height at the expense of weight. Although high density foam panels can be used to build up height, too many examples of TC floor damage where foam compressed at the edges leaves me wary of advising it. Some people have created wooden frames with foam inserts that work well, but you will still need a mat over the top and possibly one between the wood frame and truck bed.