
Hello!
Irene is correct; a hula hoop is a bit too inflexible for a hoop skirt and if you need to cut it, the edge may shred your fabric.
You can get bridal boning by the yard at most fabric stores. One or two rows of it ought to do the trick. You can also get boning used in Civil War reenactor clothing at
http://www.farthingales.on.ca/home.htm or
http://www.longago.com/findings.htmlif you want heavier/stronger boning for the skirt.
Saff