For my use case, Sheepshaver works great:
1. Sheepshaver can mount both .dsk and .hda files, so I have all my 68k-era images automatically mount when I open Sheepshaver.
2. Sheepshaver allows you to mount a folder ("Unix Root" in the settings) from your modern OS environment as a volume in Sheepshaver. I use my Downloads folder since that's usually where things I want to move across end up.
This means I can go to eg. Macintoshgarden, download a file, open Sheepshaver and just copy it into one of the .hda images I use (which looks like a regular hard drive in Sheepshaver).
I then copy that .hda image onto the SD card that goes in the BlueSCSI! Works great for me. It should be possible to mount your RAID as the Unix Root, and if not copy it to your local machine and mount the folder there instead.
I've added some screenshots, I'm using a Quadra 700 icon for the .hda images but they function as separate hard disks in Sheepshaver (and on the BlueSCSI).
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View attachment 76289