That exploit is still in the game?
One way around it is to make the 'no bombing' area around the base shield larger than the actual shield graphics. Say 33% bigger. it would help. Simple XML tweak.
Oh, I see. The bombs are projectiles. If the bombing run starts outside the shield and continues along a line that streches into inside the base, the bombs fall through the shield anyway. Bye bye base.
Does not the Shutter Shield (particle Shield) upgrade stop them? It is suppose to stop laser and projectiles like arty fire, rockets, and falling bombs?