Finally got my fix done.
fixed the cracks with epoxy
Picked up some 1/16"x3/4" aluminum angle
Attached it to the back with pop rivets and the center mounting screw will hold it.
You can see the pop rivets in this one.
I trimmed the top to clear the body of the camper.
Here it is put back together.
I added washers to the mounting screws to spread out the force and hand tightened all of them. I also picked up some caulk cord from Lowes to put around all the screws between the skirt and camper.
This definitely stiffened up the skirt and will reduce the flexing when traveling.