The brackets from Tegiwa for the OEM rear brace that I bought for the project two years ago had kinda low rigidity. Therefore I decided to build my own brackets.
The design is straightforward. I simply used a thicker sheet metal, about 4 mm thick and designed the brackets in similar way as the front OEM brackets. Actually I used the front OEM brackets as well. They came with the second brace bar which I got from Ebay. I cut the metal pieces that hold the aluminum bar and reused them for my brackets.
The only issue with this design is that I had to cut some small openings in the side quarter plastics.
But overall it's a lot stiffer and still rocking the OEM clean look.