By changing the polygon to to a layer mask, I successfully got a right result. And it is all I need for now. I just need to detect the position key frames ...

You can hold down the Y key (the pan behind tool)to re-position the fill inside your mask. For rotation however, I just use an alpha track matte on a mask only ...

I'm trying to design a lower thirds motion graphics template for use in Premiere, however, I seem to have trouble with getting the text to line up properly.