According to Memory Beta, caitians are 2–3 metres tall. That would have them all towering over most humans – and then what is M’Ress, a dwarf? The only other caitian depicted in film is Srrell (a background character in The Voyage Home), who is also roughly human-sized.
According to Startrek.com, the vedala hown in the Animated Series is three metres tall. In this case there is one frame of the animation in which she is standing next to a roughly human-sized person and does loom over her. So maybe vedala really are the size of full-sized tigers. No reason why they shouldn’t be. This matters to me because my character Lieutenant Commander Ruh is supposed to be a vedala.
I have introduced some new characters, Ash and Ember who I have decided are a new species just so I can make up their society myself without worrying about contradicting some FASA supplement from 1977 or a Pocket Book from 1988 by mistake. Ruh is big so these guys are going to be small—once there is some gravity so they can stand next to someone, at any rate.