Under the assumption that a missing boot sector on the disk is what is keeping it from being recognized by the OS, it occurred to me that I should be able to use dd to simply copy the boot sector (first 512 bytes) from a valid floppy disk and insert it into the already created image. This would naturally trash the File Allocation Table (FAT), but I figured one step at a time.

I imaged a known good/blank floppy, and then used dd to merge the first 512 bytes into the previously created image.

So that....kind of worked. Putting the boot sector of a blank disk into the first 512 bytes of the Disklavier image makes it mountable, but there's clearly something weird going on. Judging by the track names on the right, it seems like some data is overflowing somewhere. I tried some file recovery tools on the image, but they complained about a boot sector mismatch.

Thinking about it now, I believe the problem (or at least one of them) is that I am using a boot sector from a 1.4 MB floppy on a 720 KB image. I've ordered from blank 720 KBs as part of this project, so when they arrive I'll repeat this same process and see if the results change.