All four changes suggested via review from Mark Dickinson have been made.  One note: the else if (!(e == 0 && f == 0.0)) { change was made; this makes the Pack2 function parallel the Pack4 function slightly less.  I agree that it's cleaner this way, but I've left the original if in as a comment for comparison to Pack4.  I'll remove the comment if it's decided that it's better to be clean than parallel.

The suggested test cases were added in the v4 patch, just in case that wasn't clear.

I'm going to assume that my questions about _struct.c aren't issues unless someone explicitly says they are.

Thanks for all of the review and feedback!  :)