APM Sharepoint authentication

Here is one for you guys: i don't use adfs. I use a forms login page to authenticate users in an ldap then I get the username and do a kerberos sso. This works fine with sharepoint and Office web apps but opening office documents does not work. i have the login pop. I will need to take a look a look at the irule and try ti adapt it. if you have any hints please shoot :-)