I appreciate you said this tongue in check, but I think this is a really good point. OP - if you try this end of the day it is NOT permitted by AC (or even airport) policies and AC are within their rights to say you gotta check that.

So, by all means give it a shot, but please ensure you are conscious of the fact that it's huge and avoid bopping people on the head walking on/off he plane (Zone 5 in the Z1 line are fair game )

I'm not saying you won't do this, I just think it's worth mentioning lest you end up in another thread or two :P

Question ... don't backpacks sometimes gotta go in the trays? My goto is a 450AW and it can be tough to fit in sometimes.