I still use an external frame pack for trips more than 10 days in length or if I am taking technical climbng gear of lots of extras for fishing (total pack weight 35-42 lbs) I have a Kelty Trekker frame with extension bar, but ditched the hip belt, shoulder straps and packbag. I replaced the hip belt with a much simplier old one I had from an old Kelty. I bought new lighter shoulder straps. I simply strap on my 1-lb Granite Gear Virga for the packbag - hard to explain but just put the pack on the frame as if the frame were a person and betweeen the hip belt on the Virga and sternum strap, and two side pocket straps, I can get it very securely fastened. So my entire pack weight now is 3.8 pounds (including a large stuff bag strapped to the bottom), instead of 5+ pounds. The advantage is that once at base camp, I take the Virga off the frame and use this for my climbing pack. So I do not have to bring a day-pack. I also made a very light weight packbag for times when I do not use a day-pack. The weight of this arrangement is less than 3.5 pounds. I also have put the extension bar on backwards - makes for a great support to hold a bear cannister.

With a little adjusting, you could also put other packbags on the Trekker frame. A shoe repair shop will place grommets in different places if need be.

I felt that the hip belt and shoulder straps were way over-kill on the Trekker. Good for 65 pounds, but I do not intend on carrying 65 pounds!