I get the feeling that some license is being taken with the exact proportions of the Preservers from image to image in that they are proportional to themselves, and the height if six heads sure looks about right to me, but they aren't always proportional to their environment... the actuality might be somewhere between the two. Look at Petalwing's feet in the sketch, they're shaped much like a regular foot. But don't Preservers have a much more insectoid foot? So I would guess that the sketch was done when the design wasn't quite so set? Maybe? So we could guesstimate that Preservers are somewhere between 8 and 10 inches tall and that maybe they vary among examples? Like some are taller than others? That might actually solve our problems.