This post kind of caught my eye and this situation must be somewhat of on a PC 'case by case' basis. I've been able to successfully load larger organs of the 6 channel variety with the meter reporting as low as 0.2 GB of memory left without warning and without issue. That's what I'd call getting in by the skin of your teeth!
Yes, I will agree it seems larger sets that consume the majority of available memory do unload rather slowly, I don't know if this is due to a combination of the size of the instrument and the memory used, or what. When I had 24 GB of available memory I had one set I had to tinker with (adjust bit rate) to fit into 24 GB, and again just barely. The first time I went to unload it, things did just kind of sit there like it had hung up and I got the 'Hauptwerk is not responding' message, but it did eventually unload, I probably waited about 5 to 10 seconds for things to happen. I now have 32 GB of memory, so the set in question now leaves about 3.5 GB of memory left with the same bit rate configuration. It still unloads quite a bit slower than the other sets I have, and I do still get the occasional 'Hauptwerk is not responding' message when I go to unload it, still takes about an additional 5 or so seconds for things to happen, but it does unload every time, I've just gotten accustomed to being patient and waiting as I now know what's going on. Kind of interesting, but in my case sets that take up say 5 GB less memory in my set up do unload immediately, no wait, no hesitation.
Marc