The print is functional and has been holding up pretty well in PLA but will prabably be better in PETG for the added flexablility and enviormental durability.  Added two modified versions. one thicker at 9mm and one with a rounded hook

Tested in 0.2mm layer height with 30% or 40% gyroid infill,  the flexibility is just about right, printed horizontally.

Designed around a belt that is 40mm X 6.5mm in cross section, but should be useable to anything smaller than that with the hook. 

Thanks!