If you want to use the efficiency of a FasL4 profile you give up the functionality of decrypting SSL using a client SSL profile and inspecting or modifying the HTTP using an HTTP profile.
If you need to load balance based on HTTP content, you would have to switch to a standard TCP VIP and add a client SSL and HTTP profile to the VIP. You could then insert an HTTP persistence cookie.
An alternative would be to use SSL session ID persistence. I think this would also require using a standard TCP VIP instead of a FastL4, but it would allow you to avoid decrypting (and re-encrypting) the SSL.
Aaron