
is this what your after?
all i did was cut blanks out of the rear bumper but only up to the swage line, so i had the smooth bit and then curved thing along the top edge, then plastic welded it in with a soldering iron, (on the 3 flat sides cut the blanks about 3mm bigger than the indicator hole, you can use the excess material to weld onto the bumper, but i cut some rods from the rear bumper to fill in where needed)
now onto the hard bit, the top, the trick is to weld it from the back, can be awkeward but you can always cut the indicator mounts out (not gonna be needing them are you lmao)
to join the bits of the "tube" around the top on the front just be careful and use a thinner attachment on the soldering iron
i used normal body filler, ive even been in a crash, the filler has cracked but the welds are perfect.
hope this helps dude!!