I installed the 1-piece replica from EBMotors. The fitment was pretty crap.
Same for me -- the holes on the two ends (near the tires) were impossible to put a nut through, so I just taped it up with 30 lb. 3M tape. Has been holding up so far. I did get two bolts on each side though at the side and towards the center. Then obviously, the other 3 that screw in just like the stock one. 5 total, hopefully that will do the trick.
Even with a lot of tinkering I couldn't get the panel gap fully sorted out, especially on the left side. Any tips on getting those nasty gaps sorted out?