I am looking for a used set of panniers, basically cuz I am broke after buying a new bike for my son and myself this year! I checked out ebay and bid on a set from REI. I was just wondering about the size. I plan on using them for weekend camp outs. I am a good packer (from back packing). I guess my main question is, "is there a down side to buying a bigger pannier than you really need?" I know the dangers of more room, more stuff you can pack= way too heavy. Anything else I should think about?