Underbelly little insulation and open to rear floor truss

[AndBets]

We have a 06 Laredo 5thwheel and I have been having red squirrels in the garage area. I have since killed 3. Looking around the rig I stumbled on that the rear floor truss up and behind the bumper is open to the underbelly. This is where these squirrels are entering. Is this normal to have this part of the underbelly open since Keystone advertised this a heated underbelly? And so little insulation in there it is pathetic!!!I would like to seal this area off with aluminum screen and then spray foam the heck out of it. Thanks for the help.