Replying to Topsheets for box

I know "use the search bar"Already did

I bought some like .220? inch thick like plexi glass from Lowes and it was like 35 bucks. I build my flat downbox (2'W 8'L 2'H-and a down box. I hear countersinking but i have no idea what that is. I tried drilling through the sheet and it just cracked and i smashed a sheet with my bare hands. I didnt seem like it would slide right , it was "optix" it was the "5 times stronger" stuff. Now I wanna get some real nice , tough, durable, slidable top sheet.I know about lexan but not sure where to buy and how expensive. Money isnt that much of a problem as long as it isnt like 300$.