I have 4 of those red NRS boat bags. We have several IKs in 3 of them, and an aire puma in the 4th.
On a side note, we took 2 aire bakraft expeditions IKs up to Alaska last year, had both boats, plus pfds, paddles, paddling clothing, helmets, throw bags, pump, etc. etc. (all the paddling gear for 2 people plus the boats) in 1 duffle bag that weighed in at 48 pounds and was one of our free checked bags through Alaska.