could you give us a little more information about your setup? Is it a site that forces https, or allows both? Is there an SSL proxy on the F5?
My suggestion (w/o knowing more) would be to put the redirect in as the "fallback host" in the pool that the servers you are trying to get to, and then disable the servers from that pool's point of view -- that way, whether the traffic comes in http or https, it should be redirected.
However, if you are not running the SSL on the F5 (e.g. if you are running it on the servers instead), your architecture is probably different.
Hope this helps,
Doug
Nimbostratus