Couple of pics of one of the carb pistons.Please take the top off of one of the carbs and remove the air slide piston and photograph the bottom of it showing clearly how the needle is located in the bottom of the piston height wise.
The needles seem to be located correctly. The info on needle height can be confusing namely the sintered bush holding the needle being level with the bottom of the piston. This is not true as the bush needs to be flush with the slot in the bottom of the piston as you have yours.Couple of pics of one of the carb pistons.