Mt trailer came with the Zanterra hose carrier. It needs to be extended by a couple of feet. I think the material od choce is PVC. I measured the carrier and the interior diameter is 4.5" The thickness of the carrier puts the outside ID at a little under 5"
The wall thickness is a little under 1/4".
For you guys who have done this, which way did you go, sleeve the outside or the inside, and what size & schedule PVC did you use?