I now have a need to modify some system tables (mostly to change VARCHAR
lengths of some fields).

I'm planning to scour the archives for specific syntax that works. What I
would like to do is start a FAQ on this topic which we could post at a web
site and subsequently refer to. So, if you have a stash of working SQL
statements which modify system tables, please send it to me. I will
organize and label and comment and then publish as a FAQ list.