I sanded the scarfs on the bench belt sander, make a 90deg mark across the face to help eyball a good square end. A mark at 8" from the fence with the strip laying on the fence yielded a 8:1 scarf. I glued the scarf in place on the boat. I stripped cove up, so I placed a dowel in the cove with waxed paper under it (so the dowel wouldn't get glued) to get the joint straight. I had a tough time at the tapered ends till I used the idea that Jay described...Then smooth sail..er..kayaking. Experience, mine and other's pays off!
Have fun, Steve