OK, I'm going with a pack cover over a liner. I don't like the idea of a pack heavy with rain water, and a wet pack that I have to dry out at night.
I have a GoLite Pinnacle–it doesn't have a top cover per se, so a pack cover would help with rain striking the top of the pack.
I got the GoLite medium pack cover. It is pretty light–3.8 oz, but darn it's big–too big I think. I still need to balloon the pack up to max volume and see how the pack cover fits, but I still think it's too big (it is rated up to 5500 cu in–the Pinnacle is 4650 cu in).
Anyway, I'm looking for a more form fitting pack cover that is the same weight or lighter (roughly). I read somewhere in my research about a pack cover that had slits for the hip belt to run through–or something like that. Anyone know of this cover? It seemed to fit quite well and protect where the pack is in contact with the person's back better than most covers.
Any other cover suggestions for a cover for a 4650 cu in pack?

