Decal texture help

[The Man in Black]

I’m trying to make a mod that replaces the blood spray when an unarmed fist hits flesh with a bruise decal texture. My first test went badly. Instead of a small, mostly transparent bruise, I got a giant opaque pixelated purple blob that covered half the body. I could use some advice.

 

The texture itself is 256x256. There is a slightly different bruise in each quadrant, and I checked the 4 subtexture box in so that they would be applied randomly. They look pretty good when I tested it as a layer over a body texture in GIMP. (I am unsure if I’m supposed to generate mipmaps for a decal.) I didn’t make a normal map or specular because I don’t want it 3D or shiny, just matte and flat on the skin like a real bruise.

 

I’m having difficulty with the CK settings. How big should the min/max size settings be so it looks about the size of a fist, more or less? I selected Blended alpha, but it didn’t show up at all transparent when I hit someone. Could someone please explain what all the other values mean in layman’s terms?