My Y fillet attempt with #Blender Nurbs surf multi patch, imported in #Moi3D via Obj format and converted in Nurbs with SubD command
This is a try with Blender for G2 continuity.

Blender Nurbs Bézier patches


Moi3D sewed surfaces imported via SubD command from and OBJ


Control Points


Control Vertext of multi multi patches bèzier nurbs surfaces