Cargo hulls can make incredibly good, and relatively cheap, commerce raiders. The one HP doesn't matter when you spend all of your space on engines and one pop-gun. Sensors are a to taste kind of spice, but in general I find plunking a SWACs type hull in the area of operations, and using a few raiders is a handy way to cheaply kill off trade routes. If there's anything around that can threaten you, you can either out run it in retreat, or run circles around it.
As mentioned previously, a interesting tactic early is to arm a cargo hull with engines, and use it to explore... When meeting vulnerable colony ships, constructors, or starbases it can be very effective. Just one good mission and the thing will have paid for itself in spades. Especially with early mining stations and resources. Oh how especially they can work there.
To whom asked, he who initiates the attack, shoots first. Another important strategy. A 1 hp craft that shoots first, and destroys what it hits in one shot, wins.
Now, having said that, I don't normally use cargo hulls for warships. I rarely make them anything more than engines with a pop-gun... However. On one of the maps where I'm playing an influence or no war policy (or just to scared to go to war at that time), I will build a few cargo hulls that are max'd out with weapons... Enough to kill a station in one shot, send the ship over next to a space station I want gone (resource, influence in my territory), find an enemy of the owner, and give them the overgunned cargo hull. This usually gets rid of the station quickly enough, give me some diplomacy points, and I don't fear a 1 hp ship... Just have to remember to shoot first.
