Time to post up my FE Design fender vents.
1st pic. Mask off the fender with painter's tape. Position the template where you want it, and tape in place. Take a Sharpie and mark the inside of the template.
2nd pic. I used a 4" fiber cut off wheel on my die grinder to cut the fender. The fender is steel, unlike the hood which is aluminum. Cut on the outside of the line you made.
3rd and 4th pic's. The hole in the fender that you just ruined.
This is what it looks like.
5th pic. Cleaned the area up, and spray painted the inner fender black.
6th pic. Fitting the vent. Had to trim some areas bigger. The bottom point had to be opened up more. I used an air powered belt sander to trim more.