Thanks, so you did; seems like there are some situations where Media Toolbox cannot correct a problem (or different setup) with the RDB and OS3.1 HDToolBox can somehow "reset" the RDB. I didn't see any obvious problems with your earlier screenshots.
Good luck with the other suggestions for your final drive. Could you perhaps dump the entire RDB of your still non-working drive using a program off aminet?
Here are a couple of example programs:http://aminet.net/disk/misc/2b_RDBArc18.lhahttp://aminet.net/disk/misc/Rigids.lha
- can backup from block 0 to end of RDB, in case RDB is does not start at standard block 0.
Might in future help to uncover why Media Toolbox cannot install RDB to this drive, just in case it is RDB related. If it is too much bother to backup your existing RDB don't worry about it.