tudedude
I think your hintonii seedlings have grown quite well. The size of seedlings is good enough for grafting.
I do not have experience to graft young seedlings on opuntia. If you grafted hintonii seedlings on pereskiopsis correctly, you will get a successfull result. I think the black grafting face is not good news. I found you did not need any pressure on hard scions during grafting if you used pereskiopsis stock.
I did not have seedlings and grafted very small pups of Aztekium ritteri and Geohintonia mexicana.
Hanazono
1. Aztekium ritteri, grafted in March 2011
![Image](http://inlinethumb30.webshots.com/46109/2867105240044113659S600x600Q85.jpg)
2. Aztekium ritteri, grafted in March 2010
![Image](http://inlinethumb08.webshots.com/48455/2469530300044113659S600x600Q85.jpg)
3. Geohintonia mexicana, grafted in March 2011
![Image](http://inlinethumb18.webshots.com/48529/2696524010044113659S600x600Q85.jpg)