Essentially that's what I am going to have to do now since the installer only allows one copy of safari per PC and I can't figure out an override, even via msiexec.

   1. uninstall S5
   2. install S4
   3. archive S4
   4. install S5 to different directory
   5. unarchive S4

Oh and the reason for multiple installs is of course to test what breaks in what version. Many people won't be upgrading just yet to S5.

update: this now works great and both versions peacefully co-exist