I updated build a new spool holder since I build a acrylglass housing around my sparkcube. Pictures will follow.
The guiding-blocks will be connected with a screw for adjusting the width of the spool-guiding, to the width of the spool. Each block carries two bearings thus the edge of the spool will be guided inside a small gap between the bearings (spaced with the use of a nut inbetween). With the use of this spool holder, the spool is prevented from jumping off the ballbearings since the axis is rotated around 10°.
Test with a new spool already done. Working fine even if the filament is stuck underneath another layer of filament (due to no good wrapping around the spool).
Have fun printing!