I hit Harbor Freight during the week, get to try out my air shearers today. Think they do better on straight cuts, I'm cutting a continuous curve, will see how they do on the spare tire carrier/trunk floor.
Usually they cut curves easier one way than the other. If i want accurate cuts i put my jigsaw with metal blade upsidedown in my vise. I finally made a bracket to hold saw, gives me more control, and chips are directed downwards.
add a shear that fits in the drill and a nibbler i have all i need to cut metal in any situation.