In previous years the google melange system (the GSOC submission interface) allowed students to edit the proposal if the mentor explicitly grants permission.
The new system launched this year will not allow any edits to the proposal after the submission. Google admins clarified this change is to ensure fair competition. So you only have between now and the deadline (March 25th 7PM UTC). Note: its UTC, for those in US timezones its mid-day so you need to act very soon (read it NOW). Suresh
