My packs:

Backpacking - multi-day - Gregory Shasta, circa about 1985
Backpacking - fast'n'light - Dana Designs Racer X
BOB - Kelty MAP 3500
Deployments - MAP 3500

The Racer X is a "bagless" pack, just an internal type harness to which you attach the dry bag size of your choice.

I can't sing the praises of the MAP 3500 loudly enough, either. It is sized and configured like a very well designed day pack, but it has high quality, honest to goodness (removable) internal frame, hip belt, and shoulder harness just like a full-on multi-day internal frame pack three times it's size. It is amazingly comfortable and versatile. BTW, "3500" isn't it's cubic inches; it's a bit smaller.

It's not in Kelty's normal retail line, although you can find it for sale. It's apparently something they did for some military program. An ex-special forces friend turned me on to it, and told me it's quite popular with them (really). But it doesn't look the least bit military or "tactical" unless you get it in ACU. My tan model looks like an ordinary, everyday day pack.

Jeff