There are lots of overhead spool holders, and for good reason: Mounting the spools on the back is just stu... ah, inconvenient. Up top you can easily monitor for snags, view the quantity left, and easily reload, without climbing around the back to see what's going on. And, the filament feeds almost straight downward into the extruder. Mine first passes thru the filament out detector, the hood, my dust cleaner/oiler (a Dremel polishing wheel) and straight into the extruder; no top plate or guide tubes are necessary. Since year zero I've had my spools sit on rollers sitting on top of the fine acrylic hood I got from Dave Randolph. Filament feeds downward through the seam in the top panels of the hood. But I didn't like sitting the spools there because I've always been afraid I'd crack the hood. So its always been my plan to use an overhead holder. But none of the existing ones seem to fit, because they sit on the upper edge of the case, where it would interfere with the hood, and they were usually too short to clear the hood. I also wanted it integral to the case, not free standing. This holder mounts to the upper side of the case, and doesn't interfere with the use or removal of the hood. The spool bar unclips easily to remove and replace spools. Most of it is the trusty schedule 40 1/2" PVC pipe, which is about 0.8" in outer diameter. I used about 5 feet total, cut into three 19" pieces - your exact measurements may vary, so cut to size. The two side mounts are "pvc side holder 20L.stl" and "pvc side holder 20R"; one each for the right and left sides. The '20' refers to the degrees of rearward slant off vertical, and this can be adjusted in the .scad file. The same scad file is used for both right and left, just comment out the appropriate line to choose. The 20 degrees was just right for me so that when the side holders are mounted just to the front of the center side panel screw, it places the front edge of the spools right above the slot in the hood that the filament is fed down through. The side holders each mount with four M3-15 screws and nuts. That just clears the inside enough to mount the nuts without interfering with the belts and such. Use the part itself as a drill guide, but be careful not to the damage the wires and belts inside. The fit should work out so that the vertical PVC tubes are a snug slide fit into the holders. They shouldn't require glue or anything and are fairly easy to remove when necessary. The top cross bar (not the spool bar), is also PVC with a pair of normal PVC 90 degree coupler pieces. I think I'll glue those couplers to the top bar, but everything else can remain a friction fit to allow removal. I used a piece of scrap metal pipe (the post of an old floor lamp) for the spool crossbar. I dunno, it just seemed classier than using another piece of PVC, but you could probably use PVC there just fine. Unfortunately my pipe is 19 mm OD, and that's what the .scad file is set for, so if you want to use something else, you may have to do some work on the cross bar clip in OpenScad. An M4x25 screw holds each crossbar clip to a hole drilled in the PVC at the height/position you want. I was careful to find the largest spools I had to make sure they'd fit.