update - I decided to transfer 2 seedlings onto an old mount that I had. They are not tied to the mount, some of the roots have been hooked under the fishing line to stabilise. The parent attached itself fairly quickly, I'm hoping that these do too. I will hang the mount when they are firmly attached. If its successful, I will probably put the others onto mounts. These are roughly 1/2-3/4 inch in diameter.
The second photo shows new growths. Interestingly the leaf size is the same as an adult's. The roots in the photo went a light green when I watered them. I think one of the secrets to growing cernua successfully is that roots must dry quickly.