Trust me...if mice are your motivation for an underbelly just stop that thought right now. On my last camper I had a mouse city built inside the underbelly. It made it really hard to deal with them as you could hear them but not get a visual. It was a cold, dark war waged that winter (shudders thinking about it).
I am glad my roo has a naked belly. If the wars rage this winter I am not going in blind.