The Portable Cabin
So… maybe there is another way to anchor the cabin. If it is on two runners or even four, maybe two or four additional runners could be soundly anchored to the foundation and the cabin slid onto them using the original runners. Then the floor could be bolted to them from above as well as with metal L brackets underneath. The bolted runners would have to be on the outer edges to keep from getting lumps in the floor later if any wiggled lose, but the L brackets could attach the cabin to any central runners. With those in addition to tie downs, I would think it would be better anchored than most full sized houses.
Apparently in mobile homes, the foundation has to include cement runners or a slab foundation in Missouri partly becasue that way the tie downs are in concrete rather than dirt. That wouldn’t really be an issue if it were anchored to the foundation as solidly as a house, though. Even so, I’d use tie downs, I think, in addition to bolting to the foundation, just to be safe. Missouri has some pretty strong winds, after all.