apachemd

As I read your post I have the impression that you are still in the planning (dreaming?) stage and have decided that the osprey is really cool. Go ahead and dream, but these tiny packs are for experienced campers with the skills to use the gear that goes into them. If all you want is a justification to buy packs that aren'y what you need, go ahead - buy them by all means, this keeps gear manufacturers in business and people employed.

I went to a second hand store with a friend yesterday and helped him pick out a Lowe Alpine pack - about 6 pounds and 30 years old, but it cost $15. All of his gear can fit into it. There was a Gregory G pack there, but I told him that it was only for people with itsy bitsy camping gear, and he is a size XXL so he wouldn't even be able to put his sleeping bag and coat into it.

Buy large cheap used packs or borrow. When you have some gear, you will have an idea what sak will be required to carry it. I like my 6500 cubic inch pack because I can carry anything in it unstuffed and save the weight of the stuff sacks.
Jim