Just returned from a trip to Oz and this was also my first trip where I took my DSLR, Ike housing and strobe. I purchased two carry-on rollies, one a Pelican and one from Underwater Kinetics. Here is a link for the UK version:
Underwater Kinetics Cases
The UK model is around 2 lbs lighter than the pelican BTW.
All of the camera gear fit in both cases quite comfortably along with our dive computers and certain other goodies (lights, rescue strobes, chargers etc.) and we met the weight limitations for the Air Canada international flight. Camera, housing (with handle) and some small bits went into the pelican. Strobe, computers, chargers and other bits went in the UK model. Unfortunately we got on the plane a little after the other passengers and there was no space left in the overheads for both cases. We got one in but had to endure one stowed on the floor in front of us. Wasn't all bad though...it did make a good footrest. So try to get in the front of the line when your rows are called for loading to ensure a first crack at the overheads.
In Oz though it could have been a different story. Carry-on rules for domestic flights there call for a much lighter carry-on
and a smaller size. I didn't want to risk a challenge at the airport so I modified my setup. I left the plastic cases at a friends and carried my housing and camera in a padded backpack. My wife carried the rest of photo gear (strobe etc) in another soft backpack and we travelled easily for the rest of the trip and still met the reduced restrictions for the Oz domestic travel rules. Other friends of ours travelled with their Pelican cases but were never challenged so I could have stayed with the system I used when I travelled on the Air Canada leg as it turned out. But I am not so sure I would continue to risk it because you never know when the airlines will tighten up on this.
After reflecting on what I did on this trip I will be doing things differently in the future though. I don't think I will use the plastic cases again because they do draw attention to themselves and they are too big to conform to all the carry-on rules one may encounter. Plus, I reasoned that since all of my gear is insured for loss I should reserve my carry on allowance for things that I can't afford to lose or for things I don't want people tampering with. So the camera with its memory chips, my computer with its logged dives, prescription mask and my regulator will be coming on with my carry-ons. I think my housing, strobe etc can go carefully wrapped in my checked stuff.