The nocking point would have to be, using the shelf rest system, higher than the normal one, not less then 2/8 of inch above the 90¡ for the recurve and not less then 3/8 of inch above the 90¡ for the longbows (the special squares will help you to check that has not moved or to reproduce it on the new string).

To realize the nocking point more elegant and light than those in metal you can proceed in the following way:
Wet of glue the part of interested serving, take a piece of dracon, possibly of different color from the serving and clean it from the wax (an old string will works fine).
Make a simple knot pulling the heads a lot, then another knot from the opposite part and another one from the same part of the first one, always pulling the heads of the thread a lot.

Now, without doubling the last knot, you cut the thread to some millimeter from the knot with some sharp scissors and you burn the two heads to stop them.