After over a year of daily usage, i am really happy with this simple design.
Indeed colorfabb stuff is great quality but i prefer to use their bigger 2.2 Kg spool (instead of the regular small 750g spool http://colorfabb.com/standard-white) and that big spool does not fit in the default ultimaker spool holder.
I prefered to use my own holder with bearings.
I remember taking inspiration from other ideas on google image last year when i designed mine, probably from https://www.thingiverse.com/thing:486027 that seems to be designed for small spools.
You will need 4 brearings (16x5x8mm) and simple screws and nuts (i used some lying around on my desk)
I have posted the original freecad file, feel free to do whatever you like with it. I may be a good idea to mount horizontal bars instead of just 4 bearing in order to accomodate for other spool sizes. I did not need it.
print settings : 0.150mm layer, 5 mm brim, 0.8mm shell thickness and probably 15% infill is probably more than enough.