We have an acrylic dropboard for normal security, but I made a simple plywood facsimile, made some substantial cutouts in it and applied screening to it.
We simply choose which one to use based on the conditions we're in. If you have multiple drop boards you might choose to make one of them with screens and another with a lens and use them interchangeably as required.
".. there is much you could do at sea with common sense.. and very little you could do without it.."
Capt G E Ericson (from "The Cruel Sea" by Nicholas Monsarrat)
1984 Fast/Nicholson 345 "FastForward"