Q about usability of a Metz 40 MZ-3i
Your adapter is the correct one but needs a firmware update. you can send it in and metz will do the update. i think it is for free.
you need firmware m8 to make the 40mz or 32mz work with pre flash ttl on the slts. the newest vrsion is m9 but you need m8. every adapter with m3 and up should be updateable.
this is tested and confirmed more than once in a german community with the a55.