Noticed part of my Mazda 3 dangling when looking under the car. One of the plastic nuts had fallen off. I modeled and printed a replacement, now sharing with you in case the same happens :)
The hole diameter is approx 5.4-5.5mm, though it should flex a bit to accomodate slightly larger or smaller bolts as well. This is not really load bearing, but it should work for the undercarriage trim
Should work fine with any settings. Print the large flat circular part down. I printed in PETG but any weather resistant filament should work. ABS or PC may be preferable for this model due to their heat resistance.