I second what jfitch posted about the non-slip liner. A friend had just waxed his newly refinished Discus to within an inch of its life (including the belly), and when it was placed in the cradle without the wings and the canopy open, a gust of wind was enough to hit the rudder and tip it to the right until the canopy struck the ground. Result? A new canopy to go with the refinish and an "adjustment" in his insurance premium.

I recommend the cheap knobby toolbox or shelf liner. Get the white color. Just lay a 12 inch wide strip in the bottom of the cradle. Remember that you don't really want to let the fuse slip at all- it is a bad idea to load the glider by sliding it into the cradle. If it is that frictionless, remember that the fuselage needs very good restraints in the trailer.