Block Opera Mini users using true client IP

Ah, I see. I didn't know that about Opera Mini. I thought you were looking at the X-Forwarded-For header as inserted by BIG-IP.

Couldn't you do something like this, then:

when HTTP_REQUEST { 
if { [string tolower [HTTP::header "User-Agent"]] contains "mini opera" } { 
    if {[HTTP::header exists "X-Forwarded-For"]} {
        set real_ip [HTTP::header value "X-Forwarded-For"]
        if { [class match [whereis $real_ip country] equals BlockedCountry]] } { 
            drop
            } 
        }
    }
}