How much to cut out for fenderwell headers?

How did you get that chrome heat shield to clear your headers....I have one of those and couldn't not get it to clear for nothing.

It is close and I had too finesse a dent over the one tube but it fits.

This brings up another tip with these headers, you have to have the MC off or moved out of the way to install the left header. I would also recommend using dot 5 brake fluid, it will help if you have any heat issues and it won't hurt the paint if you were to spill any.