Moving images with videoplane before Chroma-keying through slab. Transparency

Hi all!

I'm working on a patch to blend together three layers of video with some chroma keying, scaling, moving around working together. It would be so very great if I could get this one thing to work;

How do I move a .mov around with xy-coordinates and scaling, before sending it through a slab object that performs some chroma keying to get transparency? The moving around bit I can do through jit.gl.videoplane, but when I try to route that video into the jit.gl.slab object, I loose the transparency. It seems like the jit.gl.slab object only accepts old-school matrix info, rather than OpenGL?

Below you'll find a patch where I've isolated the problem. I would be very grateful for any input ;-)

Cheers

/ Nils