Yo

I haven't done alot of scarfing, but got good results hand planing the scarfs for the ply joins for my trailer sailer yacht (thicker ply than what you would be using: 6mm and 9mm thick), but the trick should work.

If you haven't tried it already, I temporarily nailed the ply edge to be scarfed so that it was aligned to the end of the bench. Sort of a wood open samwhich. The bench under the ply to be scarfed supports the ply as you plane down to nothing and the bench underneath the ply also helps you stay in line.

I like to think that I got good, straight, fine 100% feather edges for scarfing that were pretty good (then I painted over them - duh, if only I knew what I know now, then).

Being a take the easy way out sort of person, for my s&g guillemot I just butted my panels together. This was easier, but the joins are more visible as a dark join line. I believe a good scarf could be quite hard to see, even close up. Just got to see what people think of pygmy butt joins somewhere below in this bulletin board see if I can sleep at night/be very nervous as I get into deep water.

Good luck

Pete