The known models are based on the finds at Oseberg and Gokstad, which, however, were not fully preserved and were therefore partially reconstructed based on assumptions.
Nothing precise can be said about the actual use of these stores. It's not entirely clear if they were actually used outdoors or just for Althing. Another theory suggests that they were tents. The word kramer was formed from Old High German heaping, meaning shop. Consequently, they were used in markets in natural harbors.
Since the size of the original finds would be a logistical challenge for most of us, we made them a bit smaller and therefore more manageable.