Thanks, howie. I bought some rather industrial strength zip ties at Lowe's, that claimed to be able to support 150 lbs., but they snapped when the fence post fell off the bumper when I was test fitting it.
The problem is that the X17Z bumper isn't square, it's only an inch or two wide on the top, so the 5" fence post doesn't fit flush. It wants to fall forward towards the back of the camper or the other way off the back of the bumper. I know I could get those U bolts to go up and around the fence post and bumper, but they look ugly IMHO.
A more seamless install would be L brackets, but I'd have to be 100% confident that they wouldn't fail during travel. I would never know it came lose until it was too late and it's super dangerous to have a sewer hose and fence post flying down the highway haha.
Too bad the X17Z doesn't fit the RhinoFLEX hose & fittings. I've very happy with the hose and don't want to use a cheaper 10' one (that might fit in the Sewer Hose compartment).
2016 Jayco Jay Feather X23B
2014 Jayco Jay Feather Ultra Lite X17Z (traded in)
2015 GMC Acadia Denali AWD, tow vehicle