Replacement of signout does not work

Hi everyone,

I'm new to SharePoint development and I was wondering why my custom signout.aspx is not called at all during signout. I need to replace this Standard page because of an error in SP 2013 with FBA enabled  and Windows Authtication.

Here is additional Information on this error: http://blog.lekman.com/2012/07/resolved-sign-out-from-forms.html

As I'm was asked to find a solution which only has to be applied once and will work in any part of the farm, the idea was to replace the standard signout page with one that calls the given code from the post metioned above.

The steps so far:

1. Created a new SharePoint 2013 - Empty Project
2. Add an Application Page
3. In aspx removed everything between the <asp:content> tags and left everything else untouched
4. Added a call to SignOut() to the Page_Load
5. SignOut was taken from the post
6. Deployed the whole thing
7. Powershell: Set-SPCustomLayoutsPage -identity "Signout" -RelativePath "/_layouts/15/SignoutFix/NewSignout.aspx" -WebApplication "SignoutTest - 8080"

A check with the PS command "Get-SPCustomLayoutsPage -WebApplication "SignoutTest - 8080" -identity "Signout"" states:

   Page RelativePath
   ---- ------------
Signout /_layouts/15/SignoutFix/NewSignout.aspx

Everything looks fine! But the page is never called :-( I changed the Page_Load to Repsonse.Write(...) without any success. I'm really out of ideas now.

Plattform: VS 2012, SQL Server 2012, SP 2013, Windows 2012 all with latest Service Packs/Updates

Thanks für your help in advance!