In regards to the OP's morph, I think it's looking very good.  The reason the eye lowering helps the age is because it increases the perceived size of the forehead/cranium and lowers the perceived size of the lower face.  

I did a quick search for facial proportions based on age and this paper might be of help.

http://www.geradts.com/anil/ij/vol_008_no_002/papers/paper003.html

Some good, general tips in there about the differences between an adult face and a child face.

On another note:

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OK.. I don't know if this is of any help, but since I like doing morphs, I've assembled a little pack of 8 face-shaping morphs for M4. Some to make him look younger. The thumbnail shows all 8 loaded at full, of course you can combine them as you see fit. The morphs are:...

Hiyas trekkiegirrl!  This is a bit OT but..

I've been trying to pack a bunch of morphs I made for the "Klingon" thread.  I'd really like to make them pose/injection morphs instead of just squishing the object files.  But, I'm having little success it seems.  I'm an intelligent guy but, for some reason, I'm just not "getting it" in regards to making redistributable morph injection/pose packs.  Can you point me to a good, easy to understand, tute on that?

PS - There are a LOT of morphs.. it's basically a "Build your own Klingon Forehead of the Week" morph pack.  It includes morphs for everything from the nose on up, all separate yet working together and includes two "Base Morphs" that can be used by themselves or built upon to create a more robust, intimidating forehead.. :)   Redistributing all those stripped .obj files would be "sloppy" IMO.