In the A-pillar you have to cut the metal if you want to flush mount the driver on the A-pillar cover. Unless you make a pod (like the ones you use for extra meters)
In the door the location you have pointed out is not that great as it is low and also it is not planar, someway near the door opener will be fine.
AC vent is not a good choice as the midrange driver will be on axis and can sound bright and uncomfortable. Also it is better if you have the midbass, midrange and tweeter in the same plane, in a line. |