Migrate workitems and change area path using Azure DevOps Migration Tools

Im trying migrate workitems from a big teamproject that i want to split up into several smaller teamprojects.
The area and iteration structure looks something like this:

sourceproject

• Unit 1 (i dont want to migrate)
• Unit 2 (i dont want to migrate)
• Unit 3
  • team A
  • Team B
    • Subnodes...

so in this case i want to migrate team 3. when i run my migration the area tree looks something likes this

• Destproject
  • sourceproject
    • Unit 3
      • Team A
      • Team B
        • Subnodes...

How can i remove the "sourceproject" node from the destination tree?

I have tried different fieldmappings, but they only affects the fields and not the tree.

my configuration look something like this

  "$type": "WorkItemMigrationConfig",  
      "Enabled": true,  
      "ReplayRevisions": true,  
      "PrefixProjectToNodes": true,
      "UpdateCreatedDate": true,
      "UpdateCreatedBy": true,
      "BuildFieldTable": false,
      "AppendMigrationToolSignatureFooter": false,
      "WIQLQueryBit": "AND [System.AreaPath] UNDER 'sourceproject\\unit 3' AND [System.WorkItemType] NOT IN ('Test Suite', 'Test Plan')",
      "WIQLOrderBit": "[System.ChangedDate] desc",
      "LinkMigration": true,
      "AttachmentMigration": true,
      "AttachmentWorkingPath": "c:\\temp\\WorkItemAttachmentWorkingFolder\\",
      "FixHtmlAttachmentLinks": false,
      "SkipToFinalRevisedWorkItemType": true,
      "WorkItemCreateRetryLimit": 5,
      "FilterWorkItemsThatAlreadyExistInTarget": false,
      "PauseAfterEachWorkItem": true,
      "AttachmentMaxSize": 480000000,
      "CollapseRevisions": false,
      "LinkMigrationSaveEachAsAdded": false,
      "GenerateMigrationComment": true,
      "NodeBasePaths": [
      "Sourceproject\\Unit 3",
      "Sourceproject\\Unit 3 sprint",