H'bar bags are nothing about being aero, and all about the convenience of having your stuff where you can reach it without stopping. I've got a Nashbar Elite bag which I modified the mount to put it on my canti-stud mounted front rack, like an Acorn/Ostrich/Berthoud style bag. Screw the aerodynamics... I didn't have to stop to get Clif Bars and gels while I did my long rides (metric up to double imperial) this summer. Plus, there's the comfort benefit of not having 10 pounds of stuff sagging down the pockets of your jersey. I thought it was funny when guys would comment about my "heavy" h'bar bag, then I'd see them load up their pockets with the same amount of stuff I carry in that "heavy" bag.
To each their own, though. I like my huge h'bar bag, and I like the design the OP used to make this mini-bag. The Arc'Teryx axe loops are a slick touch, and I like the flap closure; it's similar to what Ostrich uses on their bags. Very convenient for getting at your stuff, instead of zippers (the only complaint I have about my current bag... zippers.)