Here are some pictures of the Celica undercarriage...
https://celicahobby.com/gallery/index.php/category/celica-undercarriageMore specifically, here is the undercarriage showing just the front part
with the plastics cut -- to make it easier to swap out the front bumper often:
Here is that cut-out from another angle:
The two center undercarriage plastics were cut just under the radiator, but ahead of the fasteners that keep the rest of the plastics attached, leaving those fasteners untouched. The wheel-well plastics were also left untouched, and have had no problems with them after driving through several bad rain storms and driving sometimes over 100mph/160kph speeds.