I just saw this myself tonight when searching for a UBEC.
I thought from reading the description of their site:
http://www.castlecreations.com/products/cc_bec.html
that you could just use the castle link controller for the Mamba 25 ESC's with this unit as well. What do you mean when you day "another" castle link?
Have you tried it at all yet? What do you think.
I like the sounds of the flexibility it offers - and since I don't use more than 6S it would be fine for me.