I usually leave my tips a bit wider than I need them from the start and use side grooves for tillering. When I get to the final few inches of tillering I will add the overlay and then narrow the tip to its final size. That gives me a fresh side to cut in new nocks. Cutting in the nocks again is a lot cleaner than adding an overlay and trying to carve the nock in the overlay to match the sides.
Doug, the wood at the tips can be quite thin without compromising strength. I usually keep the last few inches of the tip the same thickness though. Overlays are more for aesthetic or function than strength.
