I bought some 2.2kg spools Colorfabb XT. To use them on the spool holders of the BigBox you have to change some parts a bit. In the file repository in the folder "STLs" is a "production" folder with a file "rear_cable_bracket_for_production_spools_x2.stl". This is a vertical cable guide for the back side replacing the two middle spine parts so the production spools have enough space: The upper one is normal, lower is the production one. I altered it a bit and added some fillets so it prints a bit better. But when I mounted that parts and placed the spool on the holder I realized that I had another issue: As you might be able to see on the image the spool is very close to the back of the BigBox. If you look at the spool holders you see that the bearings are touching the back and with the two bearings you have about 9.5mm surface for the spool to rest on. And as you can see on the picture the spool is huge and there are ribs on the side. And this is the issue. I was not able to rotate the spool freely because two screws, on the image you see the upper one, scratch the spool and because of the ribs the spool hangs and makes a loud noise when rotating. Unfortunately because the bearings are small and directly touching the back you cannot move the spool more away from the back. So I designed a spacer based on the shape of the inner spool holder: This part fits between the back and the stock spool holder and moves the bearings 7mm away from the back: It is also a little bigger on the upper side so the spool cannot slip over the bearings. To mount those I unfortunately had to open the bottom plate... And you need longer screws. Instead of the M3x20 I used M3x30. This is the result: The spool is now guided between the spool holders and not by the back of the box and away from the screws. It remains the spool holder clamp. I also designed a replacement part for this because after that mod the clamp is a little to short to reliably fix the spool in the middle: This is basically the stock part but longer by 10mm. To mount this you need a M4x40 screw instead of the stock M4x30. (Can't post a picture because I didn't have M4x40 screw, ordered some, maybe tomorrow they will arrive, then I can show).