Just beat level 5 right now. Took about 10 tries. I have screen shots of my maps that I will maybe post later on. My tatics were to concentrat the mainfiring power in a very small area and freeze the guys as they go thru, effectively sitting there while the high power towes rail on them. If they get by, my map is setup that for only a few $ I can reroute or entirely switch the flow of it causing the guys to go back thru the heavy towers. Also, when I knew I didn't need anti-air anymore, I sold it all off and used the money as a fast and efective upgrade to the land towes. Anyways,,.... screen shots to come.
PS.... no cheats either... with the NAN versionll