We knew when we replaced the horrible carpet in the Roadtrek that we would get some different mats for the driver and passenger, also. We also knew that finding something we liked would be tough because of the sliding around and unflat floor issues. The biggest area that bugged us were right where you get into the cab, because the floor slopes down a bit do to its shape and wiring harnesses, and causes the mat to be up from the floor so you can trip on it. The sliding can make it so you have to reposition the mats often, as they slide downhill towards the doors all the time.
I ordered a set of the thin, basic, mats from Lloyd, hoping they would be flexible enough to lay down all over, but they didn't. They have some glass fiber built into the rubber backing that makes then stiff, but if you overbend them that cracks a bit and they get a lot better, but still not great. They did get good enough that I figured some simple hold downs would take care of it.
I ordered two sets of VW mat hold down parts (enough for two holds on two mats). They sandwich the mat with an oval grommet and another piece screws into the carpet backing. They are a turn latch, not just a hook like many, so they physically hold down the mat and can't unhook by themselves.
http://www.ecstuning.com/ES348755/
http://www.ecstuning.com/ES348762/
Spendy, but easy to install on any mat and rug setup. I put them in the typical rear area of the mat where the OEMs put them. They took care of the sliding and some of the entry issue, but the mat was still high off the floor at the entry. I cut some strips about 1/2" wide from some .09" thick ABS sheet I had and just tucked them under the plastic door step upper flange, overlapping the mat a bit. We will see how well they stay in place, and if they come loose, I will mount them to the plastic step permanently. They hold the mat down very well along the edge.
All and all, the mats look to be held down out of the way and can't slide around, so I think we will like them. We will find out on the first long drive.