Problem I see with the hard case is identity. The quad/hexa is easily identified.I have seen how checked baggage is handled from some of the airline ground crew and I would strongly recommend a hardcase for the H or any drone for that matter. Happy flying!
From what I've heard, the backpack is just the outer shell. You need to take the shipping foam that your H came in and put it inside the backpack.
Considering this, one must ask - does this protect at least as well as the shipping box? And are baggage handlers worse on airline baggage than UPS and FedEx are on packages?