On the Rupal Face we were a team of three and found the best combination for sleeping was two people in an Alpinist Tent and one in a Alpinist Bivy Sac outside. Since I had the Alpinist Bivy  - the best bivy sac - I always slept outside. Once we climbed higher we left the tent behind and used a silnylon tarp to partially protect us, but all of us suffered many cold and windy nights looking at the stars, and more often than not the wind and clouds wip the fresh snow all over the mountain. The advantage of the Alpinist Bivy/Helium EQ combination was so obvious every morning, I would sleep well and be bone dry, while my climbing partners would be soaked from both the inside and out, a very unfortunate thing for them in that in total we climbed over 12,000 meters during the coarse of the summer, suffering and resuffering the same fate. The Alpinist Bivy breathed well and I was able to seal out the fresh snow fall all around us - this translated to being fresher during the day and me having a greater capacity for the workload. Their sleeping bags would not dry in the terrible weather we encountered all 6 weeks on the mountain - mine stayed the warmest and lightest the whole trip! For sure the best combination for alpine style available!