Using the plan from Song of the Sea, I made me some synthetic drone reeds. But they are to loud. Narrowing the air hole vent from two holes 1/8" to two holes 1/32" didn’t help. Using different styrene tonque strips .015" to 0.5" gives a different timbe but no difference in loudness. Should I use smaller tube instead 5/32" for tenor and bariton and 3/16" bass.
Arundo donax tongues will give you better sound. I never could stand the sound of brass bodies and plastic tongues.
General rule: to quieten drones, reduce the size of the inlet to the body or rush different parts of the drone bore. Reducing the air requirements by reducing the tongue elevation will also reduce volume.