I just decided to read this thread and I'm brought up in it!
Eric, yes the tips I have made a gigantic difference in the sound of the truck. A lot deeper tone and a hell of a lot louder. Mine are about a tad smaller than 6", and roughly 20" long. I have the 18" Magnaflow with resonators removed, all the rest of the pipe is stock. And when I say huge difference, I mean huge difference over the stock tips w/ resonators.