Dethermalizing with R/C
Take a look at the drawing I attached:
You need 2 of part A. SInce this part is fixed to the fin, it could be integral to the fin, and doesn't need to be this exact shape.
Part B has a tang that rides axle 1 between the 2 part A's. It also has 2 lower arms that engage the slot in part C. You could most easily make part B from sheet stock by using one "tang" piece and two "lower arm" pieces. Axle 1 is also the main axle/ carrythru for the stab.
Part C rides on axle 2, which wasn't clearly shown on the original. The slot in C, engages the 2 arms from B with a pin.
It's all just a mechanical way to provide extreme exponential.