Explicit proxy and virtual server

We are using Forti OS 6.4.12 and Explicit proxy feature. We have a server for which access is to be provided to external users as well as Internal users accessing through explicit proxy. This was working fine using Virtual IP.
The issue is that we need to fine-tune the SSL ciphers being offered. It is observed that Virtual IP's we cannot specify the ciphers, whereas if we create a Virtual server then cipher settings can be configured. However when we use Virtual server access for internal users through Explicit proxy is affected. Virtual server does not appear as destination for proxy policy whereas virtual IP can be specified as destination in proxy policy.
Is there any way for accessing Virtual server through explicit proxy or alternately is there a way to specify SSL ciphers for a virtual IP.