I've camped off the bike a number of times and the dry bags I have work fine. However, I dislike having to tie everything down with bungies and compression straps every morning and getting the bags just "so" that they don't shift while riding. Another issue is trying to quickly access things. Although that's a lesser hassle since most things I need immediate access to are in the tank and saddle bags.
I was up in Boise, Idaho this past weekend visiting a friend and stopped by Happy Trails. If you've never heard of them they're pretty well known in the ADV crowd for their USA made aluminum luggage and racks. The owner has been riding bikes for many, many years and is on site most days. Spoke with him at length and he just happened to have a rear top box with a blemish that normally sells for around $229 plus tax that he let me have for $150. I plan to use it for the 2-3 long rides I do every year around the Wind River Mt's in Wy, looping southern Utah on backroads and quick 2-3 day jaunts through Idaho. There's prob enough space in the box where I can get by with just the box, tank bag, and small backpack and possibly forgo the soft panniers. Four screws will mount it to OEM Honda rack tabs that are already pre-drilled.
Soft luggage set up
Kinda nice that it matches the fly screen
Side view
Comparative pic for scale.
With the lockable/watertight lid open. You have the option to removes the hinges and just use the latches in case you want to remove the lid when you open the box.
Ordering the mounting kit from Happy Trails. Comes with 4 small "hockey puck" rubber isolating washers that mount between the rack and the box. Nicely engineered small touch.