Adding ".ps1" to any file upload will break other parts of the system. For example, the Chef provisioner uploads a file called "solo.rb", it should not be renamed "solo.rb.ps1".

DEBUG winrmcommunicator: Uploading: /var/folders/z0/83wgqhhj04d3wmk5wrggk5900000gn/T/vagrant20130515-99727-6lta1z to /tmp/vagrant-chef-1/solo.rb

If the file being uploaded needs a "ps1" extension then the provisioner needs to add that before calling upload.