More updates on the IIcx:
-While I'm not ruling out the hard drive's reliability just yet until I've had a recap done on the controller board, since the actual spinning platter/head part seems to be fine (disk utilities aren't complaining about bad sectors or anything), it turns out that even if it's warmed up enough to boot, there's a chance that it'll stop working correctly later, resulting in weird freezes when running the OS from the HDD. I'm definitely blaming the electrolytic caps there. FDD-based operation is pretty rock-solid as long as you don't mind swapping all the time and the drive heads stay clean.
-Also speaking of the IIcx auto-inject floppy drive, I realized that this little spring-loaded arm on the left side that pulls in the floppy by a little notch needed to be bent up a bit. Now I don't have problems with the disk coming down early and not being in proper read/write position; it seems like what happened was that the arm wasn't clearing the notch as the disk carriage came down, and it sorta stayed underneath the disk and propped the whole thing up until pushed in the rest of the way. Just gotta bend it up a little more, real carefully, and now it works more or less how I'd imagine a new auto-inject FDD to work.
-I still haven't figured out what's up with the SIMM slots on this board, and it'd be much easier to diagnose if I just had a proper schematic.
-I'm getting increasingly concerned about the 6500's manual-inject FDD, like the top-side head comes down too hard and rubs off against disks, leaving marks that the IIcx's FDD doesn't despite having been cleaned. If I'm lucky, it's just a sorta smoothening and no permanent damage has been done. If I'm unlucky... well, remember what I said about disk scraping? I still haven't figured out why it's more likely to happen on the Power Mac's drive to begin with, as it looks fine, aligned, and nothing's protruding past the head.
All in all, I have a usable 68030 computer here. It's just not the most usable until I figure out how to get it to see the other SIMM quads so I have more than just 4 MB of RAM, not to mention recapping the HDD so I don't have to go scrambling for a SCSI2CF adapter right off the bat. Oh, and before I forget, gotta get a 50-pin SCSI terminator so I can use that CD drive.