[jitter] Help: videoplane or matrix for composite?

Hello,

I am not very experienced working with jitter yet, so this may be an easy question to answer :)

I need to have 3 or 4 movies in one window. I want to scale, move and crop each of it seperataly. 
For croping and compositing 3 movies, I tried with jit.matrix (like in tutorial 16).
For the moving around and scaling part, I tried jit.gl.videoplane.
My question: can I crop (define start and end dimension, without squeezing the picture however) in jit.gl.videoplane also? And: how do I get 3 or 4 movies together in one window using videoplane (is there something like "layer"?)? Whats the best way to achieve optimal performance?

Thanks for help!