I talked with him at the wooden boat festival last year. What he does is
use a router to cut a 1/2 inch slot through the hull and fills it with black
epoxy. He then uses a drill to cut a thin slot through the epoxy. He cuts
a loop of nylon strap and melts the end and flattens it so the strap won't
pull through and uses silicon grout or caulk to seal it when he pulls it
through.

Once you get the hang of it the process goes fairly quickly and the look is
really nice. Of course all of his work is beyond nice.

Brian