Some replies here, and more specific information requests.
First, I never said anything about packing a camera in the housing. In fact I explicitly said I carried my camera and three lenses in a waist bag. I am mystified why the first respondent went off on this.
Second, this is really all about weight, for me. My goal here is to NOT have to carry on a heavy bag holding a dome and housing.
So - here's the specific wish list I have. My Z9 wide angle setup weighs 26 pounds out of the water, and that does include the camera and a bunch of batteries. (230mm dome, extension, dual strobes and focus light). I need to get that dome packed into a suitcase suitable for checkin, Pelican being the case I'm thinking of. I would like to additionally put in both viewfinders, the macro port, the vacuum pump, spare o-rings and the like. Really, just as much weight as I can get in there, up to the 50 pound limit. I just hauled a 42 pound carry-on to Roatan and back, along with two checked suitcases and a waist bag. One of the suitcases only weighed 25 pounds, packed.
My goal is to find the SMALLEST (and lightest) Pelican case that will physically hold the equipment. I figure a bigger bag than is required just ends up wasting baggage weight on the bag, instead of the gear inside the bag. This is where I have all sort of issues trying to figure out what to get as I don't really have a good idea of the size of these things and what they will hold. I am currently fitting my gear into a Thinktank carry-on like this: https://www.cjcphoto.net/uwcamera/all.html
I was thinking Pelican Air 1535Trvl, but ... yes, the interior and exterior dimensions are given on the Pelican web site, but I don't see the weights. I looked up one suitcase-sized Air case, and it weighed 'only' 17 pounds. Which means I can only pack 33 pounds in that one, probably with wasted space. Hence the idea to get the smallest sized case that will hold the gear, until it hits 50 pounds.
The second checked bag will hold my dive gear, and I've been putting that in the lightest big suitcase I could find. (My late wife was an expert at finding these, but my bag is worn out now.) I'm not averse to having a second Pelican case for this stuff too, though it seems a bit heavy for gear that doesn't need much protection. Some of the 50 pounds of weight in that bag were from Nauticam parts that didn't fit in the carryon, so getting more in a Pelican for that frees up additional room in my dive/clothes bag. Which then means less for carry-on.
A key here is that I end up with two bags AND a carryon AND a waist bag. That's 3 roller bags for 2 arms. Thus I stack the smallest suitcase (25 pounder) on top of my Thinktank when I'm (literally) dragging this stuff through an airport. So a key feature for luggage is stackability, in case Pelican has some tricks for turning two bags into one for movement. Should I end up with two 50 pound checkins, my carryon will have to be light - possibly even a backpack. I doubt I'll get by traveling without a carry-on, and that's in addition to my beloved Thinktank waist bag holding camera, lenses, passport, water bottle, and some batteries.
By the way, due to the way I've had to pack, I've generally packed my laptop in the suitcase with my dive gear. One of the things I bring with me is a big 36 quart plastic cooler bag to use with the housing, and I just stick that on top of everything for padding and put the laptop inside it. TSA can't resist checking a laptop. Last trip I found two TSA receipts inside it, from the Phoenix, and then Houston overnight stop.