Shock absorbers (more properly dampers) work with the springs and weight
to control the oscillations (and also the tires). These oscillations contribute to the bucking from the trailer to the hitch on uneven road surfaces and also the sway when the wind blows or maneuvering.
The rubber suspension needs less damping than pure springs since the compliance of the rubber damps out some of the bounce and converts it to heat. This is not enough to take care of the problem completely.
AL-KO Europe has recognized this and offer the above shock absorber systems every where other than the US. The regulations in Europe encourage shock absorbers to provide better handling.
The shocks absorbers damp side to side tipping oscillations that contribute to swaying. Since the weight
of the trailer is forward of the wheel contact point the oscillations from straight bounce excites an oscillation on the hitch that is reflected to the tow vehicle.
Dampers add to the stability of the overall system and add safety to the handling and comfort to the ride in the tow vehicle. This is a large part of the exceptional reputation of the Airstream trailers.
Just because you don't ride in the trailer and experience the ride directly does not mean that the shocks do not provide a benefit to the overall package.
My decision to use the AL-KO shocks is that they have developed 4 different damping values based on the weight
of the trailer and axle. The amount of damping required varies with the spring rates and weight involved.
My guess is that that even though I am planning on using the Flexride axle since the arms can be removed to install the brackets etc. the red Octagon shocks from AL-KO Europe are probably closer tho the correct value than the single available Monroe trailer shock.
Of course this is based entirely on gut feeling and guesswork.
If you look at the video you can see that there are several top mounting positions for the shock and this allows for some tuning of the system. I don't know if these shocks are 50 - 50 % or any other ratio and neither have I found any specifications on the Monroe. The mounting on the pivot point of the trailing arm of the AL-KO mean that the compression and rebound are reverse from the Monroe mounted at the wheel hub.
I will post more information when I have the Flexride axle and the AL-KO shock absorber system.