Why not just use heat by itself to temper and reflex? Apparently sinew is a pain. I've had good success tempering bows even after they've been tillered out and have taken moderate set, the two I've done had 1.5 inches of string follow, heat treated 2 inches of reflex, and they came out flat after shooting in. And they're slightly lighter, because I had to remove wood to get them down to weight again.