Depends on what you mean by "that much". Lol.
Felt like loads when I was doing it, but the end product is pretty good i think. Have seen other Starlets with much more bumper missing.
Just have to cut a little then refit, cut a little then refit over and over to avoid cutting too much. Defo recomend having a mate with you aswell. Just makes things easier.
Worth investing in a Dremel with blades for cutting plastic aswell. Quite a few of them. Lol.