Bonjour
I confirm that the "Atoms" is a good stuff that was very popular in France. You may find bit and parts on dedicated websites as "Sail the World" (STW is a french web site!!!). I could support you on the langage.

The main issue about the trim tab is the respond delay: the wind vane turns the trim that turns the rudder...

You have the same issue with the classical "Wind vane" the wind vane turns the watervane that rotates and turns the rudder.
The respond delay is an important issue on sensitive boat (as a figarOne or a mini). A wind vane would lead to a "drunken dolphin route".
With a steady boat with high heading stability (long keel for example) the boat will smooth the swinging and it will be OK.

The main interest of the trim-tab is that there are almost no working efforts on the mecanical parts. The required resistance is linked to the breaking on board waves splashing efforts.

An ATOMS wind vane connected to a tim tab would be overdimensionned, wich is not unpleasant.

An important issue is the hydrodynamic profile of the trim tab.

Very often the trims are only flat ironsheets. They need a big angle (between 5° and 10°) to start to create a lift. With an adapted profile with a big lift to angle ratio at small angles the systems would work much better and would become much more sensible. The trim profile should be in "clear" water behind (1 or 2 inches) the trealing edge vortex of the rudder.
But, it takes more time and money to choose and build a profile than to cut a stainless-steel sheet......

An alternative would be to prepare a trim system as a back up.
Eric

STW for sale