In regards to sacking out the horse in his stall...
   I'm no expert by any means, but I do not see this as a good idea.  
The stall is too small and the horse can panick and squeeze you right 
into a wall.
   It is much better to do the sacking out in a round pen.  Once again, 
I have to go back to John Lyon's and some of his exercises.  During his 
recent seminar, John sacked out a horse in a matter of hours where by 
the time he was done, the horse had chairs under him, chairs hanging 
from his saddle, plastic tarp wrapped around his neck, ropes, papers, 
bags...you name it...and the horse just stood still.
  How did he do it?  First his basic round pen exercises.  Teaches the 
horse to trust him and that when something is scary, the response is to 
face John in the middle of the round pen and stop.  Sort of the same 
thing you would want happen in an emergency situation..say you fell off 
in front of the horse...have him stop.
  Then came the sacking out.  The more stimuli at one time, one after 
the other, the better.  First scary object...ohhhh, pretty bad.  
Second, thats bad too.  Third, well, getting kindof old.  Fourth, who 
cares?  Fifth, whose counting, lets do something else....
  Pretty amazing.  Let me know if I can help you in researching where 
to find quality instructions / tapes for his methods.
Kimberly (&Mystery the Morab)
Petaluma, CA