It's a hassle swapping filament spools in the e3d Toolchanger with the proposed holder, basically a rod protruding into the space and being fixed. The heatb ed is in the way. So I created a mounting system, with a static piece on the wall, and a spool holder which can be just dropped in from the top. The spools are not touching the acrylic sidewall, the holder is not scratching on it as well.