So I got the 12" unit mounted on the port side on the extension mount, and moved the 9" unit to the starboard side. I was able to fix the 7" unit, but now don't really have a use for it.
Went to the lake yesterday and caught a decent bunch of bass and crappie, and caught most of them video fishing. There are some big crappie just swimming in open water right now and they were pretty aggressive.
I promised a report on how much better the 12" is than the 9" on the LiveScope, and the report is that I can't say that it's any better at all. With the mount extended the full 30" the screen is reading distance from my eyes, and I don't get any advantage from the bigger screen. It has a higher resolution, so maybe someday somehow I might catch a fish that I wouldn't have caught using the 9", but I don't think it will happen often. The 9" is noticeably better than the 7". I would buy 2 of the 9" units if I had it to do over.
Once again, this is not relevant to a bass boat with the unit mounted on the deck. Your eyes will be at least 5' from the screen in that setup, and bigger is better.