How to install topshelf windows service using Octopus?

I tried the attached script but think I am having problems feeding the full path of the service executable to the script. How do you get the full path to your service executable since I am not using the traditional octopus service installer?

Got past the path issue and ran into new issue. Looks like TopShelf or a TopShelf dependency may pop a messagebox and fail the Octopus install:

Unhandled Exception: System.InvalidOperationException: The installation failed, and the rollback has been performed. —> System.InvalidOperationException: Showing a modal dialog box or form when the application is not running in UserInteractive mode is not a valid operation. Specify the ServiceNotification or DefaultDesktopOnly style to display a notification from a service application.
Error 11:30:18
at System.Windows.Forms.Form.ShowDialog(IWin32Window owner)
Error 11:30:18
at System.ServiceProcess.ServiceProcessInstaller.GetLoginInfo()
Error 11:30:18
at System.ServiceProcess.ServiceProcessInstaller.get_Account()
Error 11:30:18
at System.ServiceProcess.ServiceInstaller.Install(IDictionary stateSaver)
Error 11:30:18
at System.Configuration.Install.Installer.Install(IDictionary stateSaver)
Error 11:30:18
at Topshelf.Runtime.Windows.HostInstaller.Install(IDictionary stateSaver)
Error 11:30:18
at System.Configuration.Install.Installer.Install(IDictionary stateSaver)
Error 11:30:18
at System.Configuration.Install.TransactedInstaller.Install(IDictionary savedState)
Error 11:30:18
— End of inner exception stack trace —
Error 11:30:18
at System.Configuration.Install.TransactedInstaller.Install(IDictionary savedState)
Error 11:30:18
at Topshelf.Runtime.Windows.WindowsHostEnvironment.InstallService(InstallHostSettings settings, Action beforeInstall, Action afterInstall, Action beforeRollback, Action afterRollback)
Error 11:30:18
at Topshelf.Hosts.InstallHost.Run()
Error 11:30:18

Hi Scott,

The error stack you have provided is from Topshelf. Octopus does not handle message boxes.
You might have to get in touch with the author of those scripts to see if you can find a resolution.
It is not our area of expertise to help troubleshoot I am sorry to say.

Vanessa