Snowman9000 - If you are seriously considering installing solar panels on the roof, you probably will conclude to drill holes all the way through the roof, fill the hole with some sealant around the bolt, and then place relatively large washers on the inside to keep them from pulling back out. A member "Gary Swanson" installed a Yakima car top carrier on his roof that way
on page 45 for description.
His photo page has been taken down, but here is a picture of his ceiling showing the bolts through the ceiling -

Wish I had a structural diagram of your model 213, but all I ever got was one for my model 211. It will give you some idea on how the structural steel rafters are placed -
