We are planning a self-supported 5 day trip from Pittsburgh to DC on the C&O/Great Allegheny trail. This will be my first bike tour (although I bike a lot and I backpack a lot). I am planning on picking up rear panniers. I don't want to spend a lot until I see how much I enjoy it. Couple of questions:

1) Most of the reasonably prices panniers seem to come in the 2200 to 2500 cu inch range (e.g., Transit Pro DX). I assume that this is the volume for the pair (as opposed to each)? Is this a pretty reasonable size for that length of trip?

2) My plan is to pack clothes, gear, etc. in the panniers and strap the tent, sleeping bag, sleeping pad on top of the rack, probably in a water proof bag. Any issues with this setup?

Thanks!