I found a nice map to get the "got it covered" trophy. Mokosh Dam. To start, place 2 harvesters at an angle on opposite sides of the big starting hexagon, so they are not in a vertical line. Then race to the center tile and capture it. Against skilled not expert AI this should not be a problem. If you harvested at an angle there should be one tile on your side three hexes away from the center. Build and arm cannons on this tile and the center tile. On your next turn the trophy will pop.