This is somthing that has been done before on other spars. Just this time the holes in the rudder spar are closer to the bend in the flange. If using the dimpler, it will create an ugly crease in the spar since the dimpler die is wider than the flange and would hit the fold.
As the manual mentioned, you should grind off a little of the female die. This way you can get it in there just right and make the dimple without dinging the spar next to the hole.
I ground off a little flat edge on the dimple die.
As seen here, the die fits in just right and no hitting the spar.
