BALANCE SHIMS ARE USED LIKE WEDGES UNDER A ROCKING CHAIR. They only ride on top of the Protective shields in the ProTecTOR. Today's saddles are almost all too wide when used behind the shoulders, they are too curved front to rear as well. (If they have the same shape as your horse's back when he's standing, the above always holds true.) When using the front Shims you will find your saddle is stabilized as the ProTector's horse-shaped shields get a hold of your horse better than a saddle can. 

     When your first get your ProTecTOR, do the following exercise all in one session to adjust for the right combination of balance shims. You can remember what you felt like a moment ago. (You can't remember what you felt yesterday.) The first thing to do is remove all the shims and ride with none for a few minutes. Put the ProTecTOR pad's Label just at the back of the shoulders. (as it says.) Then cover it with the front of your western saddle's skirt or Aussie stuffed panel. After riding with No SHIMS, remove the saddle and install the #1 & #2 shims on each side in front. Put the saddle on and ride again. You are comparing your comfort (balance) at a Walk, Slow Trot or Gait. If you Barrel Race or Rope, Check your balance at a gallop, going into the barrels or against the swells ready to throw that loop.

   With no Shims: you'll find you are probably tilted forward because of your tree width or angle & curve. (That's the reason to ride the second time with 2 shims each side in front. 75% of horse/saddle combinations use the 4 shims in front. If you want to try it with 6 shims in front, do it right after the 4. Only one 1/4" shim on each side in front will lift your saddle 7/16".
     Always use the fewest shims needed for good balance.  "Go to page 11 if your horse won't maintain a lead or turn to both sides at speed. (it will tell you how to use the front shims to even your horse's way of carrying himself.)  The Reiner may find he's having Loin sorness after a week of training. That's because the back is rounding much more and the movement at the rear of the saddle has increased. That's when the REAR SHIMS come into use. They Provide the room for the rounding of the back without the horse having to lift rider and saddle with  the sensitive mid back. 

  Ropers or Reiners wanting the horse to stop better and reach with the hindquarters only have to install the rear shims.. If any rider has a STRAIGHT backed animal then rear shims are needed. 

  After a short ride with good balance attained with the front shims, pull your saddle & put the rear shims in. Get on and check your balance; if you don't feel tilted forward, then your animal & saddle needed them. You should see an immediate difference in a softer trot and head/ neck more relaxed. Also the stop should be much improved. I hope this info helps you,  Len