So I had made a habit out of occasionally one-hand gripping the tanks by putting my thumb under the part outlined in red and my fingers around the side of the tank; this let me free up a hand while not touching the film; and was also easy to transition to/from a two-handed grip.
I’ve got four tanks and haven’t had any issues; but as it turns out, that part definitely is not attached securely enough to support the weight of the tank, and I almost had a messy and expensive accident (I was 10% quick + 90% lucky) when it popped out while I was holding a full tank yesterday. I didn’t even realize it was detachable until that happened.
So, don’t do that.
I sent an email to support with a suggestion for a warning label and/or a more securely attached part.
Just a word to the wise for anybody else out there who has been doing this.