Quote - On the starting runtime, here's a trick that seems to work but has disadvantages:

Close down with the chosen runtime in place.   Locate LibraryPrefs.xml
and set its attribute to read-only.   This will also make it impossible to add or
delete runtimes, but if your overall setup is constant this won't matter too much.

I suppose if you wanted to add or delete a runtime later on you could always just
change the xml back to read/write, alter the runtimes, and then change the xml
back to read only again afterwards.