Finally got the huge drive working!!
I had to switch it to "radial" mode from "daisy chained" mode, whatever that's supposed to mean. After that, it worked perfectly. Low level formatted it using the controller card's utility, and dutifully entered the defect list printed on the label.
Got MS-DOS 5.0 installed on it, and after a network packet driver and MTCP, some FTP action ensued - I was able to log into it from FileZilla on my IBM Thinkpad A20m and load up some software, for some awesome vintage-to-vintage action going on.
This machine is very loud, very slow, and very MS-DOS.
I'm psyched.
So far I've only tested MTCP plus some games (Commander Keen, of course. Hocus Pocus and Wolfenstein 3D work, but are both too slow to be enjoyable. Skyroads works fine, however.). Tomorrow I will test Arachne on it to see if I can browse the Web usably.
One more thing: I had to switch out the Tseng ET3000AX with the Oak card I had in it originally - the Tseng started having issues (monitor was detected as monochrome spontaneously and inexplicably!). Plus the Oak seems to actually be faster, and the weird color artifacts that were there before have ceased, probably because I have a different monitor now.
I'm taking suggestions for good games to play on this computer!
World's foremost 486 enjoyer.