Been sniffing around the dragon model definition files and unfortunately I can't seem to find where size is defined on the models, other than the size of the bounding box. However, I did notice that body parts like the head, wings etc. seem to be 'equipment', separate models which are flagged as body parts...this would explain why the shrinking of size for the current models caused problems with the head attachment, and why it might not be so simple to shrink the old models, or fit proper heads on the khutits.
Unfortunately after playing around with the old Ancient model, while it is nice that they don't have a floating head problem, I still think they are way too large and their feet are far too close together... combined with the super long neck it makes them look awkward and rather like a sauropod dinosaur, which I dislike.