If you run the template against the smooth shank just below the start of the spiral part, the stack of balsa blanks will be formed just fine. I use a template of aircraft grade ply for the template and spot CA the blanks together and to the template. These CA spots are placed where I wil cut the lightening holes/wire holes in the ribs. This cutting is done by using a brass tube that has been modified into a hand-held hole saw by sharpening the end and notching. Whatever you do, be carefull. The roto-zip bits can and will eat your fingers if you are not very carefull!

Safe Flying!