Dolby Surround is a way of encoding a rear surround channel into the 2 main channels. There is no centre channel in the mix, but if you decode Dolby Surround with a Dolby Pro-logic decoder, it creates a new channel by steering any sound with equal strength in the left and right channels to the centre speaker.

I think that's right; certainly Pro-logic is a system for decoding only.

I've got a few smaller video projects to do before I start on ROTJ, so I can't say when it will be done yet. In theory, I should know what I'm doing this time so it won't take so long.

I'll post some screenshots when I have the raw video capped.