i believe joshua’s recommendation is specifically for output to multiple windows from a single card (or a single card with multiple ports, such as your gt120, or a matrox).
if you want to make use of multiple cards, you must create a separate rendering context (jit.(p)window/jit.gl.render combination), and make sure that your jit.window @rect attribute places the window in the proper display coordinates for that card’s display.
sharing one gl context across multiple graphics cards is a recipe for disaster (or at least poor performance).
you might find it necessary to re-instantiate your render context after the patch loads. this can be done easily by toggling the @floating attribute of jit.window.