Wondered if anyone knows what the best underlay for the above title is? I was looking at the Tredaire dream walk PU underlay which states its hard wearing. But other sites are saying that PU is not as hard wearing as the rubber type,which is better for stairs. Im not so much worried by the cost,just what is best. Also does it matter if you have thin underlay and carpet, already in another room, then an 11mm underlay and thicker carpet in the hallway? By this i mean will the threshold bar fix ok with 2 such different thicknesses of carpet and underlay? Any help would be greatly appreciated.