double sleeping bag or 2 zip together ones?
 

me and my wife are heading up to the arctic in 3 weeks, we would like a double sleeping bag, but it seems that all the double ones dont have a low enough temp rating, bearing in mind its going to be as low as minus 20C.... it seems the only real option is to get 2 zip together bags, but they have such a dumb shape, with that funnel shape, any input greatly appreciated....

-20C? Definitely separate bags! I don't know any "joinable" bags going that low comfort temperature while having a decent leg-space (non-cocoon type), the best ones are just couple of minus degrees that I've used with my wife. For those very cold nights we separated and added a insert layer to survive -5C or so. For -20C you need a much thicker bag that probably isn't joinable - a "cocoon" type of a sleeping bag.

The big problem is length
 

My family and I have done a lot of camping at -20 and lower. When it gets cold you want an individual bag of the appropriate length as warming unwanted foot space is not desirable. Worst case scenario is that you fold the foot of the bag underneath you to eliminate the excess. Also a thin liner to absorb any sweat will make you much more comfortable.