Citrix iApp and logout scenarios

We are currently front ending our Citrix xenapp farm with the BigIP using the citrix iApp. Using our old citrix web gateways to authenticate to citrix, our users were able to log out of the web gateway interfaces and continue working in the published app or full desktop they had loaded without being disconnected. Our new implementation using the BigIP disconnects the user from both the portal page and the current citrix session when the user logs out of the portal. Is there a way to maintain the citrix published app/full desktop connection even after a logout or timeout on the initial portal page? In addition, if a user closes their browser while logged into the portal page and their session is still active, is there a way to force the user back to that session without logging them out of their current session and establishing a new one (ultimately requiring them to re login)?

Thanks in advance, this is my first F5 implementation.

-GR