What is going on with the underbelly of this Jayco?

It may be nothing to worry about. I have had to open up the underbelly of our rig several times. Once because of a stuck drain valve on the grey water, once because the mfg put a self tapping screw through the fill tube (took awhile to find that puppy) once because the water tank was drooping- my point is, my rig is in great shape- better than new in many ways- but yes, the underbelly has been cut. And it took me awhile to figure out how to best repair it.