Because I didn't have enough space in the spot I placed my modded sidewinder x1 in, I just quickly designed a spool holder to hold spools on the side instead of the top. It slightly reduced the vibration of the gantry, but not by that much, that one could say this was worth it. Its fixed in place by the 2 existing M5 Bolts from the upper gantry part aswell as 2x M5x10 bolts with 2 M5 vslot nuts. (btw you can just use regular M5 nuts with a thickness of 2,5mm, works for me all the time). The top shouldn't interfere with the Z-Rod holders although I cannot approve this, since my modded printer doesn't have these anymore.
The Z height is definetly reduced by this mod, depending on how big your spools are. This doesn't bother me, since I don't print anything taller than 30 cm. I haven't used any spools above 1kg yet so its not sure if it'll manage to hold up that amount of weight. I haven't had any issues with it so far.
The part on which the spool rests is fixed to the mount with a printed thread, so it might be unsuitable for printers with low accuracy. In my case a bit of post processing and cleaning aswell as a drop of grease made it screw in just fine.
.stl files aswell as the .step files are provided through the downloads tab :)
Feel free to redesign this thing, since its less of a perfect fit and more like an emergency solution to me.