Kulitorum's Spool Holder

I needed a spool holder for my new printer, the DW-BOT (http://www.thingiverse.com/thing:375231) and I came up with this.
I use two different filaments, the ColorFabb filament that comes on a 50x200x55mm spool (Inner, outer, thickness) and some cheap Chinese filament that comes on a 30x150x89mm spool, and I wanted it to fit both. Also, I wanted to to be adaptable to future spools.
The idea is to screw the "Generic Screw" part to a panel in the printer, using the "Back" part as a inside off-load of material stress. Then create different "Nuts" that fits the individual spools and screws onto the screw.
So far I have printed only the 50mm Nut for my ColorFabb filament, because this is what I want to test my DW-BOT with.
I have included the CAD files in different formats, so you can load them in your CAD system.
Let me know, if you need other screw sizes for your spools, and I'll make them for you.

Replacing the spool, going from a 50x200x55mm spool to a 30x150x89mm spool.