Just popping in here to add some detail about our Aluminum undertray, which is the original flat panel undertray. As a Gold sponsor we support this forum monetarily every month which helps to keep this resource online, the sellers on social media do not. We appreciate the support in return.
Our undertray does not require drilling additional holes into the bumper to install- it uses the original holes as drill guides which accommodates variations from car to car. IF you want to however, you can add as many additional holes and screws as you want to secure the bumper or aftermarket carbon lips more securely.
On that note, our tray is a 1/8" aluminum material so the panel is just thick enough to drill and tap for locating additional holes wherever you want. Other panels are too thin so you're limited to wherever the nut-serts are placed (which may or may not be located where you need them). Thickness adds to the protection of the undercarriage, and is also a primary reason our panel is a little more expensive.
Don't be concerned about a "wave" caused by flattening the underside of the curved bumper. It is completely acceptable to secure the undertray only at the flat outer sections of the bumper cover, and leave the rounded center section unsecured. It has no effect on rigidity or function and we install them this way on customer request in our shop.
https://www.m3post.com/forums/showthread.php?t=1439553