no idea about sheep shaver or the 8.7 builds themselves
but one thing to watch out for is QEMU cant boot any Tool box rom image earlier then about the one that shipped with the G4 Cube's OS 9 install
sadly not sure why but if you try the Mac OS 8.6 Sawtooth image in QEMU (or just grab its TBXI from my My Mac OS 8.6 ramblings thread) you can see it hangs and never loads
(and the g3beige machine wont load any Toolbox ROM image at all)
I was contemplating booting these on one of my Macs. My Bondi iMac or beige G3s should be able to boot them. I haven't even downloaded them yet though.
Are Disc Copy images, that will mount in older versions of Mac OS/OS X, but not modern macOS's. You have to mount them in the classic Mac OS and run the installers.
They do boot after installed in SS, but not Qemu, Qemu just hangs trying to load the NanoKernel after OF is quiesce().
I wonder what type of patches Qemu uses to load the NK from Mac OS ROM 5.2.1, that won't work with older ROMs.
Oddly, in my attempts to get OS 9 to run on the G5 CPU in Qemu, I did get passed quiesce() to the first line of the NK log before things crapped out.