What a fantastic job! But, take your rock hammer and bust those samples down to thin section or microprobe size, Captain, or bring a mule/graduate student along <img src="/forums/images/graemlins/grin.gif" alt="" />.

A possible alternative to the external frame are these NOLS packs which are built to carry a heavy load and take abuse.

http://www.nols.edu/store/product.php?productid=16400&cat=285&page=1

They say slim is available. Not sure of the bag material. You probably would want a heavy inner bag for your samples anyway.

The Kelty 50th Anniversary is my favorite I own for weight (water for me not rocks!). It's as comfortable as I have owned for the big loads. The waste size on mine probably would not go down to 32". I am 6'2" also but haven't experienced that waste for about 20 years.

I picked up one of the Lowe Alpine prior NOLS models for $10 at the end of a sidewalk sale where they were unloading their old gear. It is comfortable, huge, will carry more than I care to very far in weight, and made from cordura which would help with your samples not skinning through the bag. Couldn't pass it up when I bartered the price but I have just used it as suitcase and fluffed up sleeping bag home bag to date. I question the waste size again on this one.

I have seen the Lowe Alpines and a few Kelty 50th on e-bay on occasion.