On a 6/12 roof gutter's outer edge of the gutter would have to be about 1/2" below extended roof line to avoid sliding ice / snow. I understand this rule is important for metal / tile roofs, but what about shingles ?

My concern is that on a 30 ft. run if I follow 1/16" rule about pitching the gutter for proper drainage AND this rule of placing gutters below ext. roof line my gutter will be 4" below the top of gutter apron and it will not cover gutter properly.

Any feedback on this one ?

Thank you in advance.