Using the term "whip" might raise some eyebrows, as it refers to a bow that has too much limb movement in the last 10-12". Some say nothing wrong with a little whip-action, but I would say most prefer stiff outer tips. But yes, your point about making the outer limb narrow is something a lot of new bowyers don't do in my opinion. Mass at the tips not only relates to slower arrow speed, it also adds to handshock. Make the last 10-12" narrow, but leave them thicker, to reduce mass and keep the tips slightly stiffer.