I was thinking something like this, it seemed that with really high currents it would be hard to cram enough copper into a 1/4 inch thick bar that was laying flat, without coming pretty close to each other. Looking at it now though it looks like it will all fit.
i was thinking of making the bars only as wide as the terminals on the IGBT's, and then making them taller to make up for the reduced width and still get the same copper cross sectional area. probably just added weight though...