In reply to Ken S:
I intend to buy an Aiguille Alpine sack as soon as funds allow and have contacted them with a couple of queries.
They've been very helpful i.e. I want a sack with an extendable lid and it wasn't clear if the model I was interested in had one. I asked & the answer was "No it doesn't but if you want we can make it to order." (at a very small extra cost).
They also said that customers generally report that their sacks are generously sized.
Don't know if this helps but I just like to support companies with this attitude.