Dave, I use a technique on all my giant scale foam wings that really makes a nice job of it. I use a long 3/8 bolt or rod that will reach well past the servo. I then heat the end with a small propane torch until it is cherry red. I have some blocks of wood on the bench to line the bolt up with the servo well and to keep the rod level as it goes into the foam. The foam will melt back to about a 5/8 to 3/4 inch hole and you will have a perfect tunnel for the servo lead to pass. You will not have any loose foam to deal with like you would if you drilled the tunnel. The foam melts and seals itself. This method works better than any other I have tried. James Goss