My bike has no rack mounts and I have no desire to continue with a sweaty back. While not against a bar bag, I prefer a large seat bag. I have a clamp on topeak, but really like the large canvas bags. The carradice SQR(I don't know the model but it's huge). Are there other bags that are worth considering? I have a brooks so loops are availabe. Ideally I could lug lunch, shoes, and a change of clothes or enough supplies for unsupported centuries.