There are a few ways to add reflex to a bow but proper,thoughtful, meticulous tillering is the only way to maintain it to any extent. Just adding reflex to a stave, no matter how you put it in, doesn't ensure the stave will have reflex when the tillering is done and the bow is shot it.
The only way I know to make a bow with reflex that will last as it was put in is to build a glass bow.