Hi Garry. Thank you for your comment. What you write about is exactly what happened to me. Spool fell down and crushed the glas on hetated bed.
I visited Prusa shop in Prague and saw them using no reductions for their printers at all. But still.. I think this is much safer way to hold the spool.
I thought I uploaded the open scad file to allow easy adjustments.
Thanks for your kind words.