Stub or Shim Process class with Microsoft Fakes

I have this code:

Have a method like this:

private void Invoke(string executablePathAndFile, string commandLineArguments)
{
    Process process = ProcessInstance;
    ProcessStartInfo startInfo = ProcessStartInfo;

    startInfo.FileName = executablePathAndFile;
    startInfo.Arguments = commandLineArguments; 

    process.StartInfo = startInfo;

    process.Start();

    if (WaitForExit)
        process.WaitForExit();
}

I am trying to stub or shim out Process class' method calls. Microsoft Fakes only creates a Stub and not a Shim (not sure why). I can provide StubProcess in a shimmed out call to ProcessInstanceGet:

InvokeExecutableAction sut = new InvokeExecutableAction(actionElement);
StubProcess stubProcess = new StubProcess();
ShimInvokeExecutableAction sutShim = new ShimInvokeExecutableAction(sut)
{
    ProcessInstanceGet = () => stubProcess
};

but when the code under test gets to process.Start() , it comes back with a Win32Exception. I am unable to provide an alternate implementation for the stub's Start method like:

Is there a way to achieve what I need (i.e. provide an alternate execution for Start() method) or refactor the code to be more testable (without going overboard!!!)?