In the 4 or 5 months I've been designing things this is the longest project I have done so far. This is a square rack mount that I made to attach some things on to the rack of my marimba. I don't know if all square racks have the same dimensions; I know it will work on a Yamaha and Pearl square racks because I have used Pearl mounts on Yamaha racks in the past (and currently). I wouldn't put anything heavy on the mounts I designed: 1 because it is plastic and 2 because it potentially hangs over my marimba. In the files are the 2 pieces to make the mount and some attachments that will fit on it. I haven't printed all of the attachments but am confident they should work. If you have problems let me know!
R1 ABS + PLA Model
More infill may be a good idea. The bottom half of the mount only needs supports while the top needs a raft and support. For the go pro and cowbell attachments a raft and support are also needed. I have only printed the go pro little guy attachment, but am confident the rest will work. I am currently designing faster than I can print and am excited to post this online. The only one with a different base that I designed is the tray; it shouldn't need a raft maybe support, but I have not printed this one yet. My plan is to ad more attachments over time.
After removing rafts and support you will need 3 bolts and nuts. A 2 inch long 1/4 thick to connect the top and bottom pieces and two 2 1/2 inch long 1/4 thick to tighten the mount around the square rack and to attach the attachments. Not difficult to put together at all; if this isn't enough help let me know and I'll make a video.