Wet sanding after cutting with a fine tooth blade on a table saw works, but is a bit labour intensive. There are special drill bits available for drilling plastics, they are worthwhile picking up, also be sure to drill the hole oversize for the fasteners so that you don't stress the hole during expanion/contraction.
We have also had good luck with Dow Corning 795.
1984 Fast/Nicholson 345 "FastForward"
".. 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)