This is an NEC Ready 9716 which I have to say is one of the least convenient cases I've worked on. To replace the CMOS battery I had to remove the entire drive cage, and the floppy cable connector is inconveniently hidden behind the power supply 😀

I'm trying to mount 2 things in the 5.25 bays that are available. The top bay with a CD-ROM is unique as it has mounting screw holes with a standard pattern, so the CD-ROM was easy. The lower 2 bays however have large open areas where I would hope to find screw holes. If they were intended to be used with rails then it's a much larger rail size than I'm used to. The only other mounting option I can imagine is some kind of server-style rabbit ears - see the holes in the front pic.

Does anyone have experience with a system like this and have any advice? At this point it seems that if the ears approach doesn't work out I'll end up kludging something together. Maybe a vecro and sticky tape solution, or something 3D printed to fill the void space in the sides. Neither sounds great.