Originally Posted by sstorkel

Hardly difficult and definitely not impossible... I had no trouble fitting a Carradice Nelson Longflap to my 54cm carbon race bike using a Bagman QR support. The only limitation is that you need some space between the saddle rails and the tire. If you've got a small frame or very little seatpost showing, you'll need to use a smaller bag (e.g. Lowsaddle Longflap, Barley, etc). The OP isn't planning to take much stuff to begin with, so one of these smaller bags would likely be perfect for him.