The 90 degree V notch is not as difficult as you think it would be. The minimum size of the V notch would be according to the illustration at center right. If extra clearance is desired then ten or fifteen thousandths can be added to the D2 dimension. Remember whatever you add to the D2 dimension half of it needs to be added to the D3 dimension. The notch is located by placing the V in the middle of the bend deduction mold lines, D1 (which is where the brake punch is located for forming). The angle between the V is 90 degrees.