I have been searching for more information about the collision hulls / entitiy min and max vectors used in c-lite.

I am trying to alter the size of the bounding box around my entity. I can do this by setting the NARROW and FAT flags but setting my.min_z for example appears to have no effect on c_move.

It appears I can do what I wish in WED by setting the polygon or bbox flag in the entitys properties.

How you do this in code?

For using arbitrary sized bounding boxes,

1) set both FAT and NARROW
2) use OBB collision detection.

Otherwise only one of the two standard hulls are used.

See: http://manual.conitec.net/collision.htm

can you still set your hull based on a particular frame of animation? I have not been using lite-c yet, as I am reading up on "c" first, but I am curious.

to find out where your hull sits and how big it is, you might use the 3d-line drawing tool. There is usefull code in the C-script template BipedPhy01.wdl, in the last part, within the the debugging stuff. It draws your ellipsoid hull around the entity, when DEBUGGING is set to 'defined'.
Not much rewriting C-script to C-lite is required to make it work.