Sounds as if your topper may be a Summit XL (eXtra-Long) model. See page 13 of this Summit installation manual
Look inside the end of the housing (usually the front end) for a label with the serial number. Then plug that serial number into Carefree's tool (Here's the link
). This will tell you the model for each slide topper. From there you can download the manuals, part lists, and the like.
I have called Carefree a couple times about similar things, and received helpful answers.