After about one and a half years of faithful service my old filament holder thing finally broke due to me overloading it and using it in an orientation it wasn't designed for. (the old holder https://www.thingiverse.com/thing:1427114)
So I made some new holders that use some 8mm threaded rod in the place where it is likely to break. As an added bonus these will print in a quarter of the time and will use less PLA.
The holders use a 25x30mm base screw distance and have M4 sized screw holes.
The base has a build in angled supports you should be able to break off with some force should you want to counter screw the rods in place. depending on orientation gravity will hold the rods in just fine tho. You can always adjust the scad files to taste.
This should be compatible with my modification of the ctc i3 pro prusa Z axis Bracket (https://www.thingiverse.com/thing:1853350) but I do not use that part in a printer anymore and only this a quick test with the bare part.
Infill density depends on infill pattern. 3 outlines recommended.