Ok,I tested this but couldn't get it to work. Presumably I didn't follow the instructions properly.
When you do changes on HTML additional headers, you have to reload the browser. I hope you did this.
With some work it could be better, so for example, I lose the hover information, I had trouble getting two of these plots on one dashboard with different bins.
For hover information, I do nit get any clue. As I never worked directly with the D3 chart.
For the multiple of charts on same dashboard issue, you might have chart id issue.
Maybe because of this one,