I just pin this here so people could think about it if ever the game gets run in the future.

This route allows to finish the level in 1:20 at best, the main time losses being first aiming with the shotgun, and also parachute jumps. If you fear to miss a shot you can still use the sniper rifle (found in a crate near the shotgun).

The first opponent worm will always skip his turn in this situation. He may or may not move. So at turn 3, you should watch for his position and place the girder in a consequent way (more frequently on the other side from what I've done)