For the Full IMAX (2.40/1.44) version, you’ll need to use the prologue from the 1.44:1 BD source, not the BB source which is cropped to about 1.66:1.
I’m compositing both sources together. This will not change the 1.44:1 aspect or framing of the special edition scenes. Here is a quick and dirty demonstration. Of course, for the actual IMAX project, the frame size will be 1.44:1 and not 16:9. This is just a proof of concept.
First, I color correct the Special Edition scene
Then, the BB scene is aligned with the special edition. The edges are then feathered so it blends into the picture better.
The two frames are composited together to keep the colors of the BB disk where possible, and where it has been cropped the corrected Special Edition frame is used.
Now this example is a bit sloppy, but I think it illustrates the point. Notice the yellow newspaper bin and the green signs especially. Both are a touch too bright in corrected frame. This way, the true colors are preserved where possible. This also rids the image of any slight haloing that has been caused due to contrast adjustments (Especially noticeable in scenes with the zipline, and the banker’s tie).