If you happen to have a CalSci windscreen be careful when doing a RR as the threaded fastener tabs on the two covers can easily be broken. It appears the slotted top hole in the screen is not an adequate length to allow the threaded fastener tab to set on the base. If you tighten the screw all the way it snaps the plastic tab. I learned this the hard way. It can be remedied by filing the slotted hole long enough to allow the plastic tab to meet the base. I repaired the broken plastic tabs with Plast-Aid.