Particle system billboard size

I have an object to which i want to add a PS. It must be a smoke texture that is emitted directly from the object's center. The object is 1 unit high and 0.2 unit wide.

The problem is that PS billboard seems to be minimum 1x1 unit. Thus it renders the smoke simultaneously on the right and left of my object (inside the billboard's bounds). But i want it to be in the center.

Resizing the PS doesnt do anything. Start size affects the textures, not the billboard.

How can i make the billboard less than 1x1 unit or how can i make textures emit precisely from it's center?