>As to your last point, you can always fire up a new Emacs process and do your highly experimental customization there I guess I didn't feel confident in my ab

>As to your last point, you can always fire up a new Emacs process and do your highly experimental customization there I guess I didn't feel confident in my ability to adhere to that policy (of making changes only to the secondary Emacs process), so what I do is keep a backup of my Elisp code with the result that emacs -q -l <path to backup init file> always opens a process usable by me.