We have a 2010 Cameo that came with a Carefree awning (electric motor). It too has 3 slots in the roller but one slot was covered when installed at the factory. I emailed Carefree of Colorado and asked if I could attach and tie down a screen to the valance using alligator clips. They said "no as it voided their warranty". When I asked "What if I was using their Colorado brand of sun screen", (exactly the same as the one I was using) they said it was OK to tie down the shade but to roll up the awning when high winds came.
Bottom line: Use plastic alligator clips to attach the screen to the valance and take down the awning/screen in high winds......Which you would normally do anyway.....Never had an issue with the motor and we tie down the screen regularly/