Hi Derek,
The hull was covered with fiberglass before I added the styrene. The styrene plate was sanded with 150 grit paper and ca thick was spread over this sanded area and then the styrene plate was placed in the correct location. I have used this method in the past and has worked well for me. I have never had any problem with water with this method. The green tape is just used to scribe a strait line on the location of the plating. I take points off the drawings and mark these points on the hull and then I use the tape to join these points and scribe a pencil line along the tale which now will give me the plating location along the hull.