I made a plate to work with Renha's Diamond hotend for Rostock. I have included Renha's part here, unaltered. Renha's part required an aluminium plate and it works with ball joint connectors. I have made a plate that can be printed and works along with Renha's part and also uses Haydn Huntley's magnetic ball joint end rod assemblies. Haydn sells his custom made steel ball mounts and provides the files for you to print your own assemblies or he offers them made to order. I highly recommend his stuff and you can see his work here: https://www.youmagine.com/users/haydn-huntley
Note, I had to use MeshMixer to do a "Plane Cut" about 3/4 of an inch up from the bottom of Renha's part in order to make room for the Diamond print head to stick out far enough. Not sure why I had to do this, but it worked perfectly.
If you need the magnetic ball carriage part to go along with this, please see my thingiverse carriage part here: http://www.thingiverse.com/thing:719276
This effector plate was made with 123D Design by Autodesk. I have included the 123D files in case you need to tweak anything.