If you would like to see an illustration of what is Mutar & Osor in the opinion of Rav Falk, he put out a Sefer that has exact illustrations as to what is considered Ervah & what is not. How far back a Tichel can be in the front, sides & also the back, when wearing a Hat.
The best thing would be to go to your Rav or Rebbitzen, and ask them what is the Minhag that your community follows.