Couple of things to add – I got one from the Kickstarter batch and got the long bracket. Since then, I got the short bracket so as to keep things more tucked in. I do slightly catch the back of my legs on it while pedalling, but only slightly so I tend to put up with it. The short bracket doesn’t have the metal band attachment either. I leave the short bracket on my winter road bike so when I fancy a long ride in to work I can easily just go for that bike.
I also use a Klickfix handlebar mount, and use the bag on that. It is fairly bulky as a handlebar bag, but works fine. I use that when I have the childseat on the back of my commuter, so can’t use my panniers.
I do put my shirt in it – I take trousers, shirt, underwear and lunch in it regularly, which fills it up but is fine in practice.