After getting the boat on the table and lining everything up, I began to tape off the sections to be scarfed. Though epoxy was a strong consideration, after more talking and reading, I decided to go with a traditional polyester resin and 1708 in 6" tape, as the average thickness of the glass is 7/32. On the sides, gunnel and deck where the glass abuts I will have a 12:1 bevel, unfortunately a wedge was cut out below the water line almost 3" wide at the keel! In this area I will use the same tape out 10" running down the hull versus across it. Actually I will lay all that in first for strength, then lay tape in one piece gunnel to gunnel to join the halves and build it back up, then finish with with some CSM over it all before sanding.
In the image above I'm still getting layers of 1708 fiberglass tape on the seam, drying and sanding between layers. In the image to the right I have all the layers I need and am starting my final sanding before fairing. There are four layers of 1708 on the keel, three mid section and two on the sides with CSM over that to help fill. There is considerable difference in thickness of the hull on the keel versus sides.
After fairing and then gel coating I will be flipping the boat to work on the top side. After discussion with a couple of people about what type of marine foam to pour between the hulls to fill the void of what was cut out and add rigidity and flotation to the hull, two marine foam companies and one skilled boat builder, I will be following the boat builders recommendation and using Gorilla Glue. As odd as it sounds, the glue when activated with water expands as a very light and rigid foam. My own experiment with it is showing that it can withstand forced submergence in water and retain excellent buoyancy.