Use at your own risk...Your milage may vary...You have been warned...Don't blame me...This is a disclaimer...etc.
I believe I have the answer to my own question. Solution is to change the umask for user applications. Outline:
- Use a file editor in Terminal to create a file called "launchd-user.conf" in the etc folder of the root directory (i.e., file is: /etc/launchd-user.conf).
- add a line in that file to read: umask 007
Now files created by ALL users will have 660 or -rw-rw----- permissions (that's four dashes at the end; 1 dash for the execute on group and 3 dashes for read, write, and execute on others). That is:
Owner -> Read & Write
Group -> Read & Write
Everyone -> No access
Other permissions can be set as default by changing the umask 007 line to read umask nnn (where each n is a number between 0 and 7). See further below for helpful references on octal notation and use of umask.
Solution above is from Apple article and carries all kinds of warnings. See here:
http://support.apple.com/kb/HT2202
I had hoped that new folders would get 770 or drwxrwx--- permissions (that's three dashes at the end), but it doesn't seem to work for new folders created by the Finder. Instead they get 750 or drwxr-x--- permissions (that's three dashes at the end) if created by Finder and 755 or drwxr-xr-x permissions if created by TextEdit (and other applications?).
Other potential solutions (that I've not looked into): Get TinkerTool System Release 2 and work in what the developer calls the "Pane System."
Helpful article (not by Apple) on octal notation:
http://en.wikipedia.org/wiki/File_system_permissions#Octal_notation
Helpful article (not by Apple) on use of umask:
http://www.cyberciti.biz/tips/understanding-linux-unix-umask-value-usage.html
