I've just returned from holiday and see Decksurgeon has announced the Sinn Ultimate U-A being initially released through THG. You can jump to the thread here:
This 47 mm cased U1 has been in the works for some time and is being made available to us Sinn Forum members for our Sinn WatchUSeek Limited Edition project (see the Sinn Forum Watch sub-forum for details). Please take a moment to vote on which case you'd like to see our white lume dialed fully tegimented U LE to have.
With this final piece of the puzzle we should be able to get this project moving again...finally.