Benframed, Mr. Hall; I looked at the video {Grafting Honey Bee Larvae for Queen Rearing}
That larva looked to me to be 48+ hours post hatch. That is very questionable.
I use a JZBC tool, the larva I graft is smaller than the lip on the tool. In the video, the larva grafted on the Chinese grafting tool was huge, almost the width of the lip that extends from the tool.
The younger the larva, the better the queen. This is the best tip I can give you: When you think the larva is to tiny to graft, to tiny to see, that is the best age,,,only hours old.
Yes, that fella in the video probably has good grafting success, with such large larva my grandmother could. But put my hours old larva against his 48 hrs Old larva and compare mature queens. My queens would blow his queens away with eggs laid.
The larva I graft is so small, I must use a stereo microscope 8X to pick up and to place larva. I have to up the size, of the larva {older} if I use a jewelers head set. Now a fella with perfect eyesite could use a jewelers set just fine.
The larva should be translucent, not quite big enough to make a perfect {C}.
Remember, older larva is easier to work, much easier, but the younger the larva, the better the queen. Some fellas use cell punch, an egg, I can?t find any fault, it works. I prefer to graft myself, just personal preference, both methods work. The end result is young as possible larva.
Blessings