Hey! After many many trials I found a max partition value tolerated by DUNE Pro 4K Plus II.
It is 16.770.000MB (Dune shows 17,6TB and Win Explorer shows 15,9TB).
All allocations was realized on my PC Win10Pro with NTFS parameter and default allocation unit. Next was tested on my Dune (if partition was to big DUNE did not recognize the disk).
Now, only 396.333MB (0,4TB) is wasted, so I create in this space a second v. small disc partition - 0,4TB.
Campus! Dune Pro 4K Plus II has his own 3.5 disc rack, so I do not need any adapter.