After a bit of trial and error, I found a pattern in this book and have made four bags so far. They turn out great if you follow the instructions (funny that). I gave one to Abby, make one each for some teenage boys (i made theirs heaps bigger than the pattern) and have a proto-type one for myself. I'm really happy with them.
Please ignore the toilet paper on the floor - why on earth is that there in the entrance way??