I can't use a trepanning tool on this because the rear seat already has holes and the front speakers are going in an area of various thickness. Fortunately I have a hole saw for the fronts and after looking at the rear seat again, I am going with the body saw. Given amount of area I have to work with in the rear, the body saw is small enough to cut near the top and bottom of the opening. I can then use the roto-zip to do any trimming necessary. I just need to start pulling the interior apart to reroute wires to the new locations. After looking at how the boat was originally wired, I am fighting an urge to rip everything out and rewire it. I used to be a machine tool electrician and everything we did was more like art work, all wires had to be straight, no twisting, everything run at right angles.