Hello Ron,
"Activate Date" has separate meaning than what you want to accomplish.
If you used "MSF Agile" template to create the Team Project, It means it will have date-time when your Work Item last became "Active".
You will not be able to use this field to have "Start Date" of the task.
However you can use TFS "Start Date" and "Finish Date" mapped to MS Project "pjTaskStart" and "pjTaskFinish" to have tasks Start date and Finish Date based on the linking(Predecessor) of these task in MS Projects. So you will not need to delete or add any mapping.
The answer to your 3rd question is Yes. You can create a baseline project in MS Project, then connect to TFS, add additional field values, like Work Item type...etc and Publish your project.
Hope this helps,
Smitha Saligrama MSFT |