Well I have made some brackets up today, see here -
http://www.mkivsupra.net/vbb/showthread.php?275510-Another-project-begins&p=3490429&highlight=trial+rear+brackets#post3490429
I basically copied the ones from the thread mentioned, but added a bent edge on one of the sides as I didnt like the design of them and thought they looked a bit flimsy against side wobble.
Unfortunatley these took me a long time just to make just one set, as I dont have the proper equipment for this type of thing and dont currently have the time to make multiple sets but if you would like the dimensions I would be happy to help