Rich, Valou, thanks for this valuable insight.   Having checked some air carrier restrictions, and knowing it is sometimes the whim of  the clerk as to "accept or check" we do not want unexpected surprises at security checkins.

Both the Adventure 9 and the smaller versions show slightly too thick for BA "template" thing but yours made it.    While many US carriers have a total measure for h, w, d, other carriers use a set dimension max for each.   This will be worked out and likely with a backpack sort of carry.