Basically, make sure the cutout around the ear speaker is large enough to expose all three sensors to the left of the speaker. I discovered real fast today what happens when the sensors are covered. 
A pair or scissors took care of the problem but now it looks kind of funky. Guess I will be shopping for a new skin.
A pair or scissors took care of the problem but now it looks kind of funky. Guess I will be shopping for a new skin.