[jitter] dimensions of a jit.gl.videoplane in the GL coordinate space

I'm trying to create a grid of jit.gl.videoplanes on the screen, but I can't figure out how to get the height/width of each videoplane (they're all taking 320x240 video matrices), so that I can use position (and scale?) messages to set them up. 

It'd be nicest if I could set 0,0 to be the upper left corner of the screen, and 1024,768 to be the other corner and then work in screen coordinates so that I don't get weird sampling artifacts in the videos, but all I really need is to figure out the size of a videoplane on the screen in its local coordinates.

anyone know how to do this? :)

-Seth