My friend just did that to his axles. Looks awesome.
Me, I am in the same place you are at. I have a new frame thatis factory primed. I was thinking a spray on liner application would be cool, but decided agaisnt this.
1. Sand off all the primer on new frame, marine clean, metel prep then POR15 rust stop/treatment.
2. Apply POR15 CHasis Coat over the primer, and just do yearly rust prevention ( rust stop inside frame rails and such ) before each winter. I am probally going to go this route. Only concern, is if primer comes off, so does the topcoat. But, its was applied and bked on, so shouldnt be a prob.
I suggest/am buying my stuff right from POR's site. Get the smaller cans, its better to use it all at once. With the smaller cans, you can get a mix and also, not just all of one. I didnt see that option in 4WD's book. Wear gloves, my friend didnt lol.
Oh, my friend loved the end result, and he tried the hammer test. Passed with no problems, and he hit it hard. Nothing came off, just a little indentation. Hope this helps.