Since I added side panels to my Folgertech FT-5, my original spool holder no longer works. This was a quick fix in TinkerCad to just cut off most of the side tabs so now it just "hugs" the sides of the 2020 aluminum extrusion. 2 Bolts hold it on which is more than enough for a 1KG roll of filament.

Update 6/17/2017: Added a 100mm length version for those short fat spools.