I only knew Leonard Zubkoff very indirectly, as a Linux SCSI guy, but he was involved in a lot of stuff during his life, including a stint hacking for Lucid. When Leonard passed away, Richard P. Gabriel gave a memorial for him. A transcript is available on Richard's website; here's a bit of it.
He looked at the design and said it was clever and could work, but it would likely take too long to figure out what my implementation was doing wrong. He suggested a quick and dirty approach suitable for a Unix-style memory manager and that we postpone the real thing until we needed it for a more sophisticated operating system.
We sketched a new design on a whiteboard and wrote down some invariants and started to code. At least, d like to think we sketched design--I think he came up with it, but he lead me through it in such a way that I thought I was contributing. Even with his simple design, it took both of us each working 180 hours over those two weeks to get it working well enough for the demo.
That was 1985. That Lisp system is still in use, having won some awards along the way, and that same memory manager is still the one it uses, though a clever ephemeral collector was grafted onto it. We were saved by the fact that a more sophisticated operating system than Unix never became popular.
The full memorial at dreamsongs.com.