by Damyon Wiese.
Hi Chester,
1. Cut off date is in that form.
2. You can set defaults for the plugin types in the admin interface - you don't need to change the code. See "Site administration -> Plugins -> Assignment Plugins -> Submission Plugins"
3. That is set in the form for that submission plugin "mod/assign/submission/file/locallib.php".
I am also working on a feature for 2.5 which will add default settings for everything at the admin level.
Regards, Damyon