Change InternalAuthenticationMethods values

Hi

I am in a situation in which Get-OwaVirtualDirectory shows me different values for "InternalAuthenticationMethods" parameter between servers (I have 2010 & 2013 CAS servers).

How can I change the value for "InternalAuthenticationMethods"?  

Resetting IIS, or making authentication changes in GUI doesn't help.

Set-OwaVirtualDirectory does not give me that option.

I want to change it to "Basic, Fba"

Would you please help?

*** I don't want to recreate the virtual directories as it is a big production environment ***

Thanks