I'm sure that there are lots of views on how best to achieve this and it will certainly be a good question for the Board. To answer your specific questions first, Tony, I do notice a big difference in sensitivity between 4 and 6wt lines, maybe not so much between a 4 and 5wt but it will certainly be there. My set-up would be for a 9ft tapered leader to around 10lbs (I like the RIO Trout, Varivas, but not the SA in this regards). Then a small tippet ring. 2-4ft to the top dropper, 3-4ft to the middle and maybe 6 feet to the point. The most important thing I find is that the point to the middle is at least 1.5 times the distance than the middle to the bob. If they are the same length I get problems with tangles and turnover.
I would not be using Flouro for two reasons, the first is that it sinks quicker (OK this is a tactic in its own right) and the second is that I never use it anyway! I'm happy to use a decent copolymer in 6lbs for tippet and have never found the need to drop to 4lb on Stillwaters unless fishing smaller flies than #16.
To keep the flies close to the surface they should be dressed with fur, fibres and maybe a sparse wet hackle. A suspender on the point can of course help keep flies close to the surface but palmers do the job fine. I never grease my leader, I believe a floating leader gets many refusals and as soon as you put any floatant on the leader it's going to get everywhere.
Many buzzer fishermen I know like to use an indicator, but you have to do some fancy sliding connections with long leaders and I personally prefer to fish with the greater sensitivity that the lighter line gives. If an indicator is required I'd make the top dropper a small Grafham Hopper or similar.
For my buzzer fishing, I like to think in terms of the adult fly (very difficult when they are taking egg laying adults by the way), Emergers (Shipmans and Suspenders), just subsurface (wets - Spiders/Palmers), a bit more subsurface (feather and fur patters, for example Cove PT), deeper still (glue/epoxy buzzers) maybe with a leaded point fly - all on floating lines. I do fish them on Intermediate lines too, but when you fish slowly you end up under the boat.
That's about all I can think of at the moment, but there are a couple of articles on Sexyloops you may not have found...
and of course the Stillwater section http://www.sexyloops.com/stillwater/ which was written rather a long time ago now! I will also start a topic on the Board.
PS My fly box usually has MANY more wets!!