Move for Larger Creatures

[Kuu]

When designing larger monsters, does Move increase with size, a fraction of size, or as a square root of size?

Or should it be modeled as Enhanced Move, since a larger creature has more trouble turning around? If so, what is the ratio of Enhanced Move to size?


The reason I'm asking this is because I notice that, in many movies and fictional stories, larger creatures are much more clumsier and slower than smaller ones. This probably has to do with the square-cube law and encumberance, but I don't know the extent to which it affects a large creature.

For example, how fast would a 40-yard worm-like creature (with ST 200, BL 8000, and weight 500 tons, that, if 2 yards long, would have Move 1) be able to move?

EDIT: Looking through Space p151, it seems that a more accurate weight would be 800 tons, as well as a ST of 233 and a BL of 5.43 tons.
EDIT 2: Going by the square-cube law, it seems that something that big would be crushed under its weight. So much for that example.