What is going on with the underbelly of this Jayco?

Toben wrote:
Hello,

I was looking at a used 27BH for sale and notice the underbelly had a hole cut in the middle and could not figure out why.

This is a 2005 Jayco 25BH at a good price.

Owner said he had it for a year and bought it from a dealer who had replaced the roof. The interior looks very nice. Outside it was a bit scuffed, but nothing surprising for a unit 10 years old.

Is it good or bad that the roof has been replaced?

Any idea why there is a hole in the underbelly?