It's over on my Experiments thread, it doesn't have its own separate one because I wasn't certain it would work. I'll find you the post:
https://www.autoflower.org/threads/elles-experiments.65694/page-29 post number 289.
And here's the video that inspired it:
https://www.autoflower.org/threads/elles-experiments.65694/page-31 post number 305 which Bushy found and linked.
He used whip grafts but when I tried that they all failed. I used v-grafts the second time: on the mother plant I cut a slit in the end of each branch I was grafting to, and cut the graft itself to a point to expose both sides to the same type of cells in the split stem.
Hope that helps!