They are spot on for 28mm.
I have eight of these mostly picked up cheaply on EBay, six Revell and two of the Zvezda Thomas version with the larger forecastle and crows nest though I fully expect some will end up with larger scratch-built fore and after castles. Nice kits, already waterlined unlike the Viking ship kits by Revell and others which is very good.
The Valdemar one looks a little odd but seems to be based more on reconstructions of the one that was excavated.
With Crusader Teutonic knights ordered I could see these being used for some Baltic crusades amphibious warfare.
I am toying with the idea of using magnets to allow the castles to be swapped around so that a fantasy version could have ballistas (I have my eye on the Warlord Games plastic Roman ones) and a historical gunship early cannon (easy enough to poodlefake from brass or styrene tube), probably breech loaders as I think that they are more interesting and quite appropriate.