This is how I diit with just one servo.
just get the 6 poins horn and plug your linkage on two adjecent horns and cut away the unused.
Hope the drawing is self explaining.
When the servo turns clockwise, the linkage on the bottom will have plenty of travel and the the one on top will have very little.
With this setup I achieve almost 45° on the bottom flap and less than 20 on the upper.