Since so many people are discussing/wondering about the size of the Mattie here's what I would say. Coming from someone doesn't really like to wear MABs on my shoulder (i find that the outer strap always falls down), I can wear the Mattie over the shoulder (b/c the drop is much longer), but the cylindrical nature of it makes it hard to put your arm down when it's on your shoulder. So if I have to wear it over the shoulder, I kinda have to push it back so that it's diagonal and behind my arm (if that makes sense). So, yeah it's possible to wear it like that, but not really functional b/c it's too wide to put your arm down, IMO.
As for the size, the compartments and open pockets on each side make the bag seem long (east to west) but the actually capacity of it in the main compartment is only a tiny bit bigger than the MAM, IMO. I don't think the bag seems huge b/c it's not tall and with the flaps back, it really shortens the length. My husband will always comments when I wear "lugguge" as he likes to call bags he thinks are too big, and he's never said he thought my Mattie was huge, in fact he loves it!
Hope that helps peeps who haven't seen this bag in person.