I printed the spool Holder featuring Emmet's Gear bearing, when I realized I had a shelve hanging over my Kossel, so there wouldn't be space for the spool. But since most of the upper middle part of the Tower is never used, I figured I can just place the spool there by tweaking the spool holder's mount. after some iterations, here's the result. You need some M3 by 8 bolts and some M3 nuts for this to hold, although maybe not all holes have to be used. I use this on a Kossel XL and I guess it won't work on a Kossel Mini. If you find it working for that one too, please tell me so I can update this description.