If you only managed to generate 2 Force points, you could opt to hurl a smaller crate (Silhouette 0) which would set the difficultly at 0 purple and 1 setback die (from the droids' ranged defense of 1).
I disagree with this. If you fail to roll enough Force points you fail. You tried to hurl the object but were unable to get it that far, you don't get to ret-con your Action and go for a smaller object.