The old plastic really emits a bad odor when cut or grinded.
Looks like a big hole but actually I tried to make it as small as possible, keeping in mind that the panel and the roll bar have to be installed as well. Of course this hole cannot be left like it is, even though the rear bench will not leave many angles to look at it once everything is installed back in the car.
So i formed a piece of plastic board to cover the hole. The plastic is easy to work with, you can form it under a heat gun, once cooled off, it retains its shape.