You have three choices.
1. Create a child table to hold auxiliary information, but then be fully aware that it will get very difficult to have a Project Report which will show data from these fields or filtered on data from these fields. So it is not likely that this is the best solution.
2. Have a separate Section on the form for the new fields.
3. Have a separate form and then the users will need to use button to see that form or to edit on that form.
#2 is the best approach, I feel especially knowing that the 2017 road map shows us having tabbed forms in the late Fall.