Parametric MasterSpool with thread

Hello, I'm using a Prusa i3 MK3 3D-Printer and refill filament from http://www.dasfilament.de.
The refill filaments saves plastic and shipping weight/costs. To use it, I will need a master-spool. I found several, but no one met my requirement, e.g. customizing the rod hole diameter or using less material and printing time. So I decided to make my own thing, starting with an other thing: https://www.thingiverse.com/thing:1782398
My thing is fully reconfigurable using openscad (http://www.opensc