Trying to figure out my pack system for 5 months of traveling through Argentina, Bolivia, and Peru. I will spend several weeks in Patagonia doing all the main treks, the longest being the Torres del Pain circuit (~8 days)

Right now I have a Gregory Baltoro 75, which is big and heavy.

Because I am not just trekking, I'm also going to have more clothes like jeans and cotton shirts for wearing in cities and other activities. I'm thinking I'll bring a main pack of 60-70L to use for my treks along with something similar to an Osprey Talon 22. The big pack will carry most of my stuff for the plane and all of my bus travel. The day pack will be used to keep in my lap with all my valuables. I will store my big pack at hostels while I go out on day trips with my daypack and when I do my multi day treks with my big pack, I will use the day pack to store my extra stuff like my jeans and other clothing. How does that sound?

For my main pack, I'm considering the ULA Circuit (talking to Chris now about sizing, any thoughts?). The problem is that I'm leaving in 2 weeks and don't have all my gear so I don't know how much volume I need nor exactly how much my gear weighs. Using weights from online, I think my base weight will be about 17-18lbs. I don't think I'll ever be carrying more than 5 days worth of food (for the TDP circuit I think I"ll carry food for a fwe days and then just spend the money to eat at the refugios).

The heaviest and largest items in my pack will be:
Scarp 1 (no crossing poles)
Canon DSLR (1 body + 1 lense and accesories)
REI sub kilo down bag
Thermarest xtherm

I'm obviously not ultralight and don't think I'm ready to go frameless. What do you think about the ULA Circuit for an 8 day trek with base weight of 18lbs? I'm a little worried about the space. ULA's site says it's 70L but that includes things like the mesh pockets (main body is only 2,400 cu in.). The Catalyst is a bit larger, heavier, and made to carry more weight. Or maybe I should stick to something like an Osprey Atmos 65.

Just googled the scarp 1, and it weighs 48 ounces from TT. You can shed a ton of weight off that with another tent.

You should read these articles,they include gear lists,trip reports ect.
You should contact Danny Milks and Kristin Tennessen who wrote the articles,Danny is a member here and has a blog here
this article is nice because they evaluate what they brought.

Edited by annapurna on 12/25/2012 23:08:13 MST.

I would take a lighter tent but the majority of my camping will be done in Patagonia where there are extremely strong winds. I need something strong enough for the winds

There can be strong winds in Patagonia, but for the tdp all campsites are quite sheltered from the wind.
From your post i think a catalyst would be a safer option.My wife bought one for trips with her huge winter sleeping bag ( 900g of down...) and she can still store 2 weeks of food + all her gear inside.
A reasonable if not UL 1.3+kg / 48oz for a very comfortable backpack.

I actually just spoke to Chris and he also recommended the Cataylst because in the past people have had problems with the carbon fiber frame of the Circuit breaking while checked on flights. It's 9 oz heavier but worth it for a stronger pack