I have never been happy with the slightly bizarre design I first decided upon for the traversers. This worked using the shiny sides of hardboard and allowed them to move by facing the base of the board and the base of the traverser with the shiny sides. The system worked, but the hardboard bowed far too easily. Thus a trip down to the local homebase (for other things as it happens) occurred and I purchased two sets of ball bearing based runners. These have been mounted to the struts underneath the traversers and although over long (not a problem as this can be hidden once the boards are installed), they will work far better.
Now to redesign the hidden sidings boards around these!