I read a bunch of tutorials on using square plastic fence posts, some with a length of gutter inside to make a sliding "drawer" of sorts. They looked pretty slick. I hemmed and hawed and made do with they cheapy tiny/thin sewer hose that would fit in the original location in the side hatch door. Not ideal.
Then one day I was at an RV supply place, and just impulsively bought an "overpriced" ready-made one (the horror! When I could have made one!). For me it was the right move as I soon had it securely attached in place of the factory one, and it holds my big/nice sewer hose easily, with room and diameter to spare.
I now use a Valterra Dominator sewer hose. It's a "premium" type and works great. The best part is that it stays "crinked" together unless or until you expand it. So it is very short in the storage tube, and then you only "uncrink" the length you need at a given dump station (vs. wielding an ungainly, long hose when you don't need it all). No complaints at all. The holder is the Valterra EZ Hose Carrier. I think I have the 64" long one, but I'd have to double check to be sure. I offset it slightly so it is easier to reach from the driver's side (but it does have a "door" on both ends). I'm not sure whether or not adapters would fit into the tube, but it's pretty large diameter (larger than the stock one) so maybe worth checking.


My original hose tube was held on by some long hose clamps, but they didn't work all that well. The middle was "fortified" with a failing bungie (not by me). Ugh. For the new holder I bought two large Fernco type plumbing connectors just for the rubber "sleeve" part. Something like this:

(No photo of the zip ties but I got them at Lowe's, IIRC.)
I wrapped the Fernco sleeves around the carrier (snug fit) where I was going to put the attachments. Then to hold it on I used multiple huge (very high load, UV protected) zip ties in the grooves where the hose clamps were designed to go. (But before you get scared to drive behind me, these are like the mother of all zip ties and rated for a LOT of weight, plus I have multiples - total overkill.) I'm sure it's more secure than the original hose clamps, and so far (around two years) it has not budged. I didn't use the little "feet" on the EZ carrier that they expect you to use because they didn't line up with anything; hence my use of the rubber sleeves, etc.
I'd do the same again, with both the hose and the storage tube.
I've re-purposed the hatch and short tube as a readily accessible compartment for disposable gloves. Mine was clean, but you can buy both new doors, and/or put on a new PVC tube (just fits onto the back of the specialized door) if you want to do this mod but yours has had a sewer hose in it.
The hatch is like this and is meant to put any 4" PVC or other tube onto from the back side. This one is made by JR products. You can typically get them with thumb latches or locks; I like thumb latches.

I'll see if I can add a photo of the holder in place, but the weather is miserable right now (pouring rain) so that's for another day.
