No I haven't and I wouldn't even consider it if you're talking about putting it on the underbelly. R10 is 2 inches thick. Well over $30 a sheet if you can even find it. Attachment would be very problematic as would removing it to move the unit.
Wedging it around the perimeter might work. I've seen people do this when I was living out of my fifth wheel for work in the winter.
Anything that reduces airflow under the rig helps fight the cold.
My plan this year is to put hooks along the edge and suspend/strap old hospitality sheets to the ground around the rig. This may well keep the mice at bay, will have to see.