Num,
The concept of the diorama is good...Soldiers checking out a tunnel and the tunnel rats seen entering the tunnel on top and getting ready to exit downhill. However, you have two M151s up top which would have had to have made noise getting there. I really doubt that the Viet Cong would remain outside in sight of any Americans once they heard those vehicles coming. You might want to rethink the posture of the Viet Cong in this situation. They would either be running, hiding, or attacking with the Americans so close, not just chilling at the bottom of the hill. Chances are that if they were just hanging out like they are, one of the Soldiers up top would see them and take them under fire. Just a thought.
James