Help - tailgate inside plastic cover bolt locations?

I have a small dent in my tailgate, and I was thinking I could maybe access it from the inside to tap it out, so I pulled the plastic cover off. Unfortunately, I can't really access the area with the dent since there is no hole in the tailgate metal frame there. Went to put the plastic cover back and I see that 6 of the bolts are different from the other 10. These have bigger heads with wider washers and are also longer. Can someone have a quick look and post up where those 6 bolts with the wider washers go? I looked at the onlline tailgate parts and it doesn't show that detail.... at least that I can find.

I may have another go at this some time by using a hole saw over the dent to fit a metal drift in to tap it, with a dolly on the outside. Stupid dent isn't big, but it is a sharp crease and will need to be worked from the inside.

 

OK, I think I found it in this diagram. The 6 bigger bolts go across the top. They show these in the upper right hand corner of the schematic.

https://autoparts.toyota.com/products/product/cover-tail-gate-ser-657590c040#popup-1