Arlon, all I can tell you is we have plenty of members here and even more on the CasitaForum and CasitaClub that have this model.
This is on the image I posted from the Casita
"Our alternate floor plan with available top and bottom bunk bed is an equally efficient choice."
On edit: Arlon we have a topic Family Friendly Floor Plans
and this is info posted there:
The Casita is a popular trailer, and rightly so. Both the 16 and 17 foot Spirit can easily sleep 3 and the optional side couch/bunk can sleep 4. The side dinette is not available with the optional side couch/bunk and the upper bunk has an 80 pound capacity. The side mounted location of the bunk bed may complicate the screening of that section of the trailer. An exterior shower is available.