Update: Updated the BIOS to A17 and did a fresh re-install of Sierra. The latest bootpack works nicely except no WI-Fi/BT. Had some strange issues experiencing the SSD not being recognised but after win10 installed nicely, 10.12 found the disk too.
Updates up to 10.12.6 without issues, Clover 4297.
Many thanks go to Jake one more time for helping and doing a great job with the bootpacks! Thanks man!
Rocking on with Fishman TriplePlay!