this is build diaries
I remember someone posted before showing that they made small cuts along the bumper to fit metal strips and on the inside you fiberglass flanges on top and below each strip. When done you can finish cutting the rest of the bumper off.
Don't know what happened to the thread.
Cut it with anything man there's no wrong way to do these things lol you sand the edges after.
dremel, skill saw, etc. careful not to cut your flanges tho
can bond metal flanges but need to make sure you have adhesive that you know won't come undone