I was just considering a single remote for the ability to shift the flail left and right, what advantage do multiple rear remotes offer with a flail?
For a standard 3pt flail you don't need any unless you want a hydraulic top link to better tilt the mower fore/aft when in use. For a side shifting flail (one that can just shift sideways) you need one rear remote A-B pair. Now for my Maschio Giraffetta 160SE swing arm verge or ditch bank mower, you need two set of rear remotes (A-B and C-D). One set swings the unit sideways the other tilts the head for the roadside bank. If I had a third set I could use my hydraulic top link to raise the mower higher and adjust its pitch easier.
It used to be for me I thought I did not need any at first. I bought my new tractor without, even though they had a screaming deal at the dealer for them. Then I added one and quickly added the second as I found equipment I wanted to run and make my life easier using hydraulics. Its like potato chips - one or two is not enough.

I'm not a young guy any more and the hydraulic top link is a real pain and time saver. Now if you want top and tilt on your 3 point, you need 2 set of remotes - the second is for the side arm control where I how have a crank handle. You can use a top and tilt to angle a rear blade by lowering or raising one lower 3pt arm. Most of the time we all have both lower arms the same height to keep things level.
When I first came to TBN and started learning and went through the hydraulics forum and saw the power beyond set ups some folks had with a dozen remotes :shocked:

(slight extension of truth) I could not understand the need. Now I know that having the extra set, or one set with float, how important they can be to do work and make things easier
The best example I can use is my IH 1300 sickle mower that I added a hydraulic bar lift too. The 9' cutting bar just got impossible for me to lift. So one set got the bar to lift. I was still using my manual top link to adjust the bar pitch when cutting. Depending on the hay I was cutting I had to adjust the pitch up or down several times to get the cutting right. This got to be a real pain and I about gave up using the mower. Then I got the hydraulic top link from Brian and used my second set. All I can say is WOW - the mower worked well again as I could tweak the top link (adjusting the cutter bar pitch) on the fly to solve any cutting issue. The same for my drum mower - I can adjust the pitch on the fly to get the best cut.
I hope this helps folks
Keith