With any type of rust prevention material like por15, durabak, rhinolining, etc the major key is prep, prep and more prep. It may be labor intensive but the more time you spend in prep, the better the rust prevention material will work.
[COLOR=DarkGreen][FONT=Century Gothic]All the Jeeps I've owned
79 CJ5 258 six with a weber (current vehicle) T18/Dana20
81 CJ5 258 six (driven out of Alaska thru Canada in winter with a softtop)
75 Jeep Wagoneer 360V8
79 Jeep Cherokee 258 six