We took a MEC Apollo (a 3-person tent) for the 5 of us. This resulted in an amazing 600g per person of shelter – and it’s still a full double-wall tent! However the main issue is not as much the room as it is the flimsiness of the tent. MEC Apollo is not really built for the arctic, that’s why it’s so light. It broke at the first sign of light breeze. In a place with stronger wind (such as Denali or Wrangell St. Elias) this tent could have been lost altogether.
The condensation was also an issue with 5 people sleeping in such a small space. A lot of moisture resulted in damp sleeping bags for those sleeping at either side. We took turns doing that.
I experimented with Vibram Fivefingers for river crossings. The conclusion is mixed. When the sun is shining, your boots are dry and you have to cross 1-2 small creeks per day, it’s certainly worthwhile to pack a pair of these, especially at just 270g of weight (for the SEEYA model).
However, if you’re already totally soaked under heavy rain; or you have to cross multiple streams so changing back and forth will take up a lot of time; or the streams you’re crossing are strong enough for you to want extra stability – there is no going around wading with your boots.
The lightweight SEEYA model is really built for running. In the icy water my feet got cold really quick. Vibram has a special neoprene model, but it weighs much more.