Yep I just got done installing this Sport bumper and finally figured it out!
I actually bought a complete, used G550 bumper from a parts seller on eBay, and then had it repainted and paint matched. This was much easier and more efficient than trying to piece together all the vents and small parts of the bumper new.
This bumper right here is very similar to what I bought, and you can see that it is near complete: https://www.ebay.com/itm/OEM-2016-16-ME ... SwvApaKH-L
I also picked up a G550 specific bumper support bracket, but it didn't have any legs on it to attach to the frame, and to this day, I still can't figure out how it goes on. DON'T BUY THIS. I then bought an OEM G63 bumper support bracket (#4638800103) and it has the legs and works great with the Sport bumper.
If your G currently has a center mounted oil cooler, you'll need to fabricate new brackets to mount it on the bumper support like I did.
Lastly, I picked up an OEM Distronic blank cover to fill in that large hole in the center opening from an eBay seller in Russia.