UAG and ADFS

Hi all,

We have a ADFS farm without ADFS proxy. We use TMG as a proxy.
We also have a UAG environment. External users can get to the intranet from UAG. 
The intranet is published on a trunk with AD as the authentication method. 

On the intranet a URL is added pointing to an application on a RP side. How should i configure everything to it will work?
Can i add ADFS as an authentication repository just like AD on the same trunk, and then create a trust between ADFS and UAG? Or should i always have a dedicated trunk with ADFS as authentication method, holding the ADFS application?

Thanks.