RE: Serving length??
If it is a 3D shooter and they request it (the need for speed thing) then I usually make it avout 4", 1 1/2 " above and 2 1/2" below the nock point. For hunting bows I usually make it about 6", 2" above and 4" below. I got into the habit of a little extra on top as more upward pressure is on the serving (nock) so it won't slip but have never had one slip.