No primer. I applied it directly to the cleaned powder-coated frames and the Lexan lenses.
Don't know for sure how it would work with old Lexan, but if its cleaned down to bare material I don't see why it wouldn't hold.
It's silicone-based so it's flexible, but unlike the Silicone caulks you get at Home Depot, it has significant adhesive strength.
It's the only thing holding in those hi-rise glass pane windows!
Its very sticky/messy, so it requires a lot of masking everywhere to insure getting a clean job.
Kgorby, are you sure it's lens that's leaking and not the hatch gasket? Those gaskets get old and hard, and will leak a lot. New ones are available and easily installed via their preinstalled adhesive backing. One trick to be aware of before installing the gasket is to measure and cut it to length, and then super-glue the cut ends together before installing the gasket. If you don't do this. it will leak at the butt seam.