Serv-U MFT enable Multi-Factor-Authentication via NetScaler nFactor

Due to the Serv-U MFT product not offering Multi Factor Authentication (MFA) for our external sites, we are trialing Citrix nFactor authentication in front of Serv-U MFT to enable this functionality.

Basically the architecture looks a bit like this..

1. Internet Facing Load Balancer hosted on Citrix NetScaler with MFA (Multi Factor Authentication) enabled via nFactor authentication mechanism.

2. Post authentication (MFA) at the NetScaler via nFactor, the user to logon to the MFT website (without being prompted for creds again -- basically single signed-on).

I have no issues with point#1 to work. But SSO to MFT application part seems to fail me. (The user is being prompted to re-login again at the MFT logon page)

Anyone tried such config and if so, would appreciate if they could share their experiences please...