Temporary solution:
Increase the size of the town by 4 times, increase the number of acks on town to double. 6 acks defending a 4 times larger area would be the picture I see. Limit VH spawn points so they don't always spawn crazy to every direction in a web(in real life, a spawn point placed inside a canyon would never ever spawn vehicles to all directions, would it?) so the direction of advancement by GVs is predictable.
Large enough so not even a three-lancaster formation with 14x1000lbs would just knock out the town in one pass. How many people you know can knock out 6 acks concentrated in a small area in 1 pass? For the average skill level, knocking out the town itself is gonna need at least 4 pilots for 5~6 minutes, provided none of them get shot down by the ack.
Four planes buzzing consistently around a field is going to draw someone's attention. If that doesn't draw anyone's attention to stop milk running, then it's not the map that is wrong.
