At what group size is it worth packing a separate cooking tent ?

Personally, I reckon one large geodesic dome able to sleep at least 4, maybe 5, would be far better value. Under Arctic conditions having everyone in one tent will bring the group together far better than splitting into two tents, plus (bonus) you will be warmer with 4 people in one tent compared to just 2 people.

For a long trip, a 2.2 m square dome would be comfortable. Slightly larger would be spacious. Note: geodesic dome, NOT a simple pop-up dome. Geodesics have many more poles.

As for having a separate cooking tent, WHY? Far, far better to have the heat from the stove(s) inside your main tent. And you can have a chief cook and an assistant, which would be very useful when cooking for 4.

My 2c
Cheers

Seems like I have seen a tent – maybe Hilleberg – that is essentially two, two-person tunnels connected by a large tunnel vestibule. Something like that would seem to me an ideal situation for four people in arctic conditions.

You would need to be able to get out the side of the connecting tunnel vestibule. You don’t want the people in the upwind tent opening the windward door (in a storm!) or having to climb over the people in the downwind tent.

Advantage: separable, and suits two couples. Could be cozy.
Disadvantage: much heavier than a single 4-man tunnel, and it needs a much longer tent site. The latter could make life quite difficult at times in alpine country.

Cheers

Decades ago a connecting tube/sleeve entry was very common in HA climbing and Arctic/Antarctic travel. The first American Everest team used specially made Eureka Timberline tents that could be connected in various combinations, one of which was a fly  to join two tents, I don’t think it was a success above camp1 due to the extreme wind and the difficulty of aligning the two tents correctly, the tube however seemed to work. One tent for sleeping the other for cooking and gear storage.

Things are different on the tundra, no space problems on the tundra and the Helsport site has a few pictures of smaller tunnel tents set-up with both covered with very large tarps but I have not seen pictures of tunnels joined like that but I like the idea very much

You can connect Hilleberg Atlas tents together.

See: http://us.hilleberg.com/EN/tent/blue-label-tents/atlas/

Of course, each one is an 8-person tent, so not exactly what you’re looking for…

Climbers on Denali seem to use group tents when the party size exceeds 6 people and looking at pictures it seems that they mostly use Black Diamond Megalites. I am guessing tho that this is probable a cost benefit choice not because they are the “best” tent to do this with, the MSR Twin Brothers is out of production and the large 3F A-tarp from China is a bit too big.

Roger the Hilleberg Saitaris is just a little too small for 6 big people with Arctic sleeping bags and the group may swell to 6 people and the other pair in the group already have a suitable 2 man Hilleberg they will be using ;a Tarra

http://us.hilleberg.com/EN/tent/black-label-tents/tarra/

I would have used my own Fairydown Plateau but it is old and at the end of its useful Alpine life

Interesting tent, the Tarra. I watched the video of a guy pitching it – in fine still weather. I am of course biased, but I reckon he just might have a few more problems in a howling storm. There would be some very dangerous flapping before he got it up.

Cheers