I like the concept of the Andinista but it doesn't really play out in real life. I borrowed a friends and have used it a few times.
It's a big sac, about 5500 cubes, so, you load this all up with gear to fill it, rope, and half a rack, and you're easily busting over its intended 30 lb limit and the thing feels like you're carrying the Eiffel Tower on your back. It's a really tall pack.
So, then, you zip it all up, and guess what, it's still a really tall pack, just really skinny. Because of the serious lack of helmet room, you have to just consider any kind of volume capacity above the load lifter to be wasted, in either its expanded or compressed state, if you're going to wear this climbing the steeps.
A good solution (sorry for the repetition) is a McHale SARC with P&G bayonets that you can use to drop the pack height for climbing if needed. Even with the P&G's in, you can bring the top pocket back a little and give yourself plenty of helmet room. I demo'd a P&G S-SARC a few weeks ago and this versatility was incredible. Cinch it up with compression straps, and you have a great option for hauling in a monster load while still compressing to a reasonable alpine day pack.