NetWare 6.5 with BM 3.8

A customer has a client 2 site VPN and has enabled Proxy access with
SSO/clntrust locally. On the VPN client he has to login to the proxy
by a
SSL screen.
Till here everything works fine, but he asks if he can bypass the
authentication on the VPN client. I personally don't think its
except turning out the proxy server in IE but does anyone can help me?