Choke thermostat problem

Hello Dan
If I understand correctly, when cold, the thermostat spring push onto the choke flap to close it and when hot this push slowly decreases.
In parallel, the vaccum pod pulls onto the flap to open it.

In my case, the push doesn't decrease. At least, not a lot. The flap isn't fully open, but rather 1/4 open, and 3/4 closed.

I have the 1970 FSM (sadly not the 1971 one) and page 14-122 it talks only about "2 notches rich". I don't see any other adjustment.
I will check tomorrow if any adjustment is possible

About the gasket, effectively it's thin. Around 3mm. But I have 2 or 3 other gaskets. May I pile up them to obtain the right height?