I'll come in on the sanded scarf side. With a disc sander in the table saw, I can clamp two strips together and knock out a scarf by eye pretty quickly. I then superglue (gel formulation) the scarfs with spring clamps for 10 minutes or so and then apply the strip to the boat. I've never had one fail on me, but I do try to put them where they are not really stressed or twisted. I'd guess my scarfs are between 4:1 and 6:1. The only draw back is the superglue can leave a darker joint line on lighter colored woods. Ok, Ok, the other draw back is you can end up gluing yourself to the strips :-) No, of course I've never done that! I've just heard about it from a friend of a friend ......

Bill