This is a derivative of LawrenceJohnson's reel holder, designed to fit wider and smaller diameter PLA reels (92mm wide x 37mm ID)
The reel holder was also made smoother.
1) Print two arms, one holder, and one end. I used 35% fill for the arms and 20% for the rest (0.2mm layers, 2 skins, and 5 perimeters)
2) Place arms in bracket on back of Ultimaker.
3) Place holder on arms with larger radius section in notches nearest the back of the Ultimaker.
4) Place reel on holder.
5) Place end piece in notches at end of arms.