This is my updated Version 2 of an impossible pass through. I upped the amount of splines from 6 to 8. 

Printed in Orca Slicer on a Bambu X1C with a Smooth PEI Plate.

Layer height .16mm

Three walls 15% Gyroid infill

No supports on the tube piece.

The insert piece I used supports with Bambu Support for PLA set to snug on only the bottom edges that curve upwards

My Speed Settings for this print:

I uploaded the 3MF file from Orca slicer for those that use Orca slicer.