Hiking with a camera backpack

Hello,
I am looking for suggestions to lower the weight of my camera backpack or possibly buy a smaller pack or belt pack.. It is a Lowepro Nature Trekker and in it I carry a 1Ds mkII with a Canon 70-300mm, a 100mm Canon macro, a 28-135mm as well as a Canon 20-35mm. My tripod is a Manfrotto 055 aluminum with a pro pan/tilt head. There are other miscellaneous items in the pack as well.
I will be leaving 2 of the lenses home, namely the 100mm macro and the 20-35mm but I will substitute extension tubes for the macro. There was a time when I could carry the pack for 6 hours or more but I am 63 and time is catching up to me. If any of you have suggestions to lighten the load still further please let me know. I am looking for a CF tripod that is light but price is a concern. Your ideas or suggestions will be most appreciated. Thank you.

Tim

I'd probably suggest losing the 28-135, keep the 20-35. You have some duplication on the ends of focal range both top and bottom. If you are worried about the gap, sub a 50 1.8. Its a mixed bag, but its sharp and practically weightless.

I use the Lowepro Primus AW for packing light on nature treks and traveling. I wrote a review of it here.

tamrac expedition series should do fine for you. It even has a padded waist belt so that it will be comfortable.