On the 2003 Rev of the Uniform Inspection Sheet (#34282C) from my Cub Scout Leaders Book it says:
"Webelos Scouts have the option of wearing the oval-shaped Webelos badge by itself on the tan shirt only; or the diamond-shaped Webelos patch along with other rank badges on either the tan or blue shirt; or it the Tiger Cub patch was earned, the Webelos diamond-shaped patch may be worn on either the tan or blue shirt by itself and centered on the left pocket."
Seems like they covered them all! The version of the Uniform Inspection sheet at scouting.org is the B version (2001 version).
http://www.scouting.org/forms/34282.pdf