Get a pro to remove the original super taikyu sticker (heatgun + sharp blade etc) off the bumper, get it reproduced, and keep the original somewhere (maybe on part of the brake ducts you've already trimmed?). Paint the bumper, put the new super taikyu sticker back in its original location
Keep the carbon undertray somewhere displayed prominently and special in your garage. At the speeds you do in WA circuits, it will be of almost no use to you anyway so no point installing it on the car. Trim the bare minimum off the bumper to get it to fit, as doug and I mentioned, unless you're doing a proper track day where you will be out for 5+ laps they are of no real use anyway.

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MY93 Impreza GX 1.8L, 0hp, 0nm