When running Triple Option, the Playside A is responsible for #3 (run support).
Here is Triple Option versus Triple Stack with the Playside A blocking #3.
If the Playside A cannot block the overhang, the Playside A will make a “LION” call to tell the Playside Tackle that the Playside Tackle is veering inside and has Playside Linebacker to Free Safety. Now, the Playside A blocks the Playside Linebacker to the Free Safety. The Quarterback is responsible for canceling the overhang because #3 now becomes #2 in the count.
Have your Playside A load when he can’t block #3 in a Triple Stack defense.