I make all my own gear and have a pair of pannier that I am very proud of. I plan on posting directions to the backpacking light webpage this summer after I'm done with this semester of school. So far my opinion is that saddle bag designs are very secure, but my next version will be attached with nylon webbing and a tri-glide (like a climbing harness). Eventually I might try the Arkel hooks. Althought I've never used or seen them, I like the Arkel hooks a lot. My design is a lightweight stuff sack with a gear sling holder. They are very lightweight and incredibly convenient since you can take the stuff sacks off but leave the pannier body attached to the bike. DougMT.... Pack cloth is pretty hard to go wrong with. I use it in all my backpacks for the bottoms and it holds up incredibly well.
Unfortunately compared to the variety of designs and directions of backpack, tents, sleeping bags and especially stoves, there seems to be a minimal of "make your own" panniers on the net. If things go as planned I want to post my designs and help that out. I would post a picture but I don't have one yet.
scott