If anyone has a question and asks a "professional" and this is the best they can do... don't bother using them. Not a parts vendor, not a machine shop, nothing. EIther a person can tell you the why for a particular concept, or they really don't know the why and got lucky or copied someone. Just like the irritating ignorant 4yr old with "why? why? why?" if the pro can't guide you and explain the whys, move on.