To bond to old fiberglass boat hulls--say to install a tunnel--what is the best way to bond?

make a template for the desired shape and width of the tunnel, draw it out on a heavy type brown paper of very thin luan. just remember you can draw half of the shape then flip it as to insure everything is the same on both side of the center line of the boat. make sure you make a mark on the forward and aft of the template dead center. to find centerline of the boat measure from chine to chine make the marks and line up the template of your tunnel. then using 4 in high speed grinder and a cuttting wheel cut it out, dont worry about stringers and such at this point. main thing is to see what you have to work with when the glass is cut. ie where you will need to cut the floor to have access to your inside laminations and new stringer work. there are alot of steps involved after that but nothing very hard to do!