Originally Posted by
zombietooth
There is only enough room in the overheads for 2/3 of the pax to stow rollaboards so, yes the overheads should be reserved for rollaboards or larger bags. I am 6' 3" and always stow my backpack under the seat, whether I have a rollaboard or not, and it isn't uncomfortable IMO. I never fly in anything less than E+ though, so maybe it would be worse in the back.
I assure you that at 6'3" it is uncomfortable, at least in my experience, to have a backpack underneath the seat in front of you in a non-E+ seat. And many of my UX flights have no E+ seats so my knees are pushing into the back of the seat in front of me unless I can use the underseat space for my legs.