I thought I read that levels that were received as a gift did not count towards earned levels that can be gifted to another linked account. I may be wrong, but I think Blizz did it this way to prevent chain leveling.

The best way to do it is to grant levels as normal, and just live with an empty spot on #5, or xfer a toon there. I think a lot of us who are boxing were playing before they discovered multiboxing, so we have a few alts already.