The tape stuff sounds like a good idea, but it has its down sides. The reason why bushwackers dont use the tape is they are trying to give you a factory look. When you use tape, it creates a gap between the fender, and the flare. Have you ever seen the guys driving down the road with the stick on hood scoops? It is really obvious that it is stuck there, and not real. I think you would be much happier with using the screws. They will draw the flare flush with your fender.
God Bless.