We use acrylic (and absolutely NOT Lexan). Slightly tinted, your choice. Just google the pluses and minuses.
The panels on our cockpit roof were 6mmm and cracked. Not thick enough.
Side windows we used 8mmm and 10mm for the top hatches (the ones we step on).
Reciprocating saw or table saw, sandpaper for the edges.
Beware of the acrylic chips, they will fly everywhere. That plastic is electrostatic and sticks to your hands, arm, hair. Keep a vacuum running.
John Bernard "JB" Duler
Meltem # 19, Western Med