dimensions of polyhedrons

Hello all,

I have sets of points in (x,y,z) that represent polyhedron vertices 
(actually tree crowns).  I have used convhulln to estimate volumes (the 
shapes are not necessarily convex, but good enough for now). Now I would 
like to extract various dimensions of these shapes - horizontal width 
(max, mean), vertical depth (max, mean), and other metrics.

Are there any packages/tools in R that might help me do this?  A look 
around didn't come up with anything.

Thanks in advance,
Allie