Try attaching guard to the top of the bucket, simmular to the guard that they have on fork trucks. The guard will keep things from coming over the top of the bucket and falling on the operator when the bucket is up high. I may not stop the little stuff, but the big ones won't get you. I think some 1/4" x 2" flat bar, some bending, and some welding would do the job. You might also consider making quik mount brackes for the guard if you don't want it installed all of the time.
