The problem with relocating the stock bumper is that the tow ring sticks out through the rectangular hole in the back. If you move the bumper up, you have to cut that strip below the tow loop. Here's a bumper that's been cut below the tow ring, just for ilustration:
[Linked Image]

PHIL

1991 HZJ77, 1999 KZJ90, 1999 UZJ100, 1992 M101CDN2
https://www.thegearheadproject.com/category/jdm-journeys/