I used exactly one 1 meter length M8 threaded rod, cut in three pieces: 2x370mm 1x260mm
Replaced the original back-top M8 rod of your Prusa i3 with the 260mm rod. Used the other two 370mm rods as diagonals.
4xM8 regular nuts
6xM8 self locking nuts
2xM5 self locking nuts
4xM3 self locking nuts