SM Install - someone who does know how it works
I was one of the support team for the core skills project that rolled out SM 5.1.1 across Birmingham between 1997 and 2003. Unfortunately since the project ended in 2003 RM have upgraded SM several times and, as you say, have little interest in supporting old versions.
Do you have a full set of CDs in addition to the floppy disk?
The installation is started from the "Basics" CD - the license floppy simply contains a list of the components in the various licensing packages. You will also need a license code and Link2ICT can supply that and a full set of installation documantation - you just need to reach the right person since all the people who knew the ins and outs of SM have move to other areas. Try asking for Ken Bearman to be notified about the call (you have raised a call haven't you?).
If my install notes are something that people would find useful outside the BGfL I could post the docs on the BGfL Connectivity pages.