Here's a 24incher Fatty I just made for my friend Chris. I'm calling it a Fatty 'cause it has a larger bottom than it normally would. I haven't made a whole lot of 24-inch bags...I think every one has been different...but a standard sized 24incher would have a 17x7 bottom, or 15x9. This has a 18x9 bottom. So with a standard or traditional messenger bag, it would usually have a 27-inch flap....blah, blah. It's big. Also: fourteen inches high, with a fourteen-inch flap.
Padded back & floating liner, of course.
Got me some fancy reflecto buckles from ITW Nexus. These are the only two I've got. If I want reflectors on the buckles I have some 3M trucker tape I slap on there. That way you can replace it when it gets all scratched up. But these are fun.
See that loop down there on the bottom? Last time I was in Chicago I saw this old army pack (a great inspiration for me) with loops on it like this. Hot damn, I thought. And here they are.
These'll come in handy if you want to carry a big box under the flap. There's one on the other side...so run a line across the box from loop to loop, and then close the flap over the box. If it's a real big box you might need extension straps.
Chrome has little loops like this under the flap on some of their bags specifically for box-carryin'. I think it makes more sense to have them on the bag. That way you can use 'em for other things. But that's just me.
I think I put them too far to the edge though. Next time I'll move 'em up a bit.