btw, I was thinking about your case issue and I have a pelican 1560 case that I use for my P2, batteries, FPV.. it's dimensions are carry-on size, plus it has wheels and slide out handle. 20.37" x 15.43" x 9.00" (51.7 x 39.2 x 22.9 cm)
Depending on the accessories you have with the phantom, and lens you want to have on your DSLR, you could probably squeeze it all in a case like this. In the photo, instead of having the batteries where they are, put a DSLR sitting on it's back, lens up.. Batteries might have to go in a checked luggage anyways i think, but not sure..In any event, one also could move the batteries around and make space for all of it I think.. Good idea too, because I travel a lot with a DSLR.
I love the case. Durability and protection is not a question, and you can customize the inserts. A new foam insert is 20$ I think. Having 2 inserts for different needs, situations might work.