The wife and I use four XS Sea to Summit compression sacks: one her clean clothes, one mine, one our dirty/wet clothes, one for on/off during the ride clothes. Following that plan, you'd have three XS sacks. We have a medium one that holds both our sleeping bag and our tent. If the tent's wet, we put a plastic bag between it and the sleeping bag. We also use waterproof panniers. There's no problem with using a compression sack with down. That's what you're supposed to do. Just don't leave it there when you're not touring. Ours gets aired out/laundered after a tour, depending on smell, and then stored in the huge cotton sack it came in, very fluffy.