4ʹ1ʺ - Snarf (measured to top of ears)
4ʹ2½ʺ - WilyKit
4ʹ4½ʺ - WilyKat
4ʹ10ʺ - Lion-O (child)
5ʹ0ʺ - Mumm-Ra (mummy form)
5ʹ1ʺ - Jackalman (measured to top of ears)
5ʹ3ʺ - Monkian
5ʹ7ʺ - Slithe (measured to top of spines)
5ʹ7ʺ - Cheetara
5ʹ8½ʺ - Panthro
5ʹ9ʺ - Tygra
6ʹ0ʺ - Jaga (6ʹ6ʺ to crest of helmet)
6ʹ2ʺ - Lion-O (adult)
7ʹ5½ʺ - Mumm-Ra the Ever-Living (8ʹ2ʺ to crest of helmet)
Though the publication He-Fan mentioned might not be as canon as the show, it's the only clearly-stated source I've heard of on the matter. It conflicts only slightly with the visual evidence I've been working with, and admittedly I don't know for certain that the line over Tygra's head means anything specific. Based on the stat he mentioned, I could scale them all down a bit. (If it's possible to upload images, I'll gladly share the one with the lines I've drawn on it.) What do you think?
Edit: Updated with more accurate measurements!

