Thanks for the replies
Might go to the counter and see what they say. Apparently you have to check in there on a basic economy fare if not checking a bag- some scarlet letter .....
I think it's easier to get away with the oversized personal item as its a backpack but we'll see. I'll report back.
On another note, is that basic economy crap coming to any more airlines? Haven't had issues with this carry on on super cheap Asian /European carriers.