I only have the Micro VGs on my 68 T337C (no Robertson kit), so can only pirep on that part by itself.
The difference in (most
of my landings is incredible....the flight characteristics are that you get nice easy control (not sluggish at all) all the way down to the ground. As a point of reference, I do approaches at 85, full flpas, and cut the front engine on very short final (ie threshold assured) to slow up a bit, and then usually cut rear engine just prior to round out...this gives me a little more air flow over the stabilizer/elevator/rudders until round out...with the micro vgs on the plane and this method, I make very nice short field landings even on long runways, very consistently.
I really should know what the VGs took my stall speed down to (yes they did definitely reduce it), but don't. sorry. I will make that a priority to go up and do some stall tests at some point. But I think it supposedly reduces stall speeds by 3-5 kts.
Again, flight characteristics of the VGs - thumbs up. Would do it again.