How to forward requests to subfolders in pool?

The best way to do this, if you're actually intending to change the protocol as well as the URI, is via a standard HTTP redirect. This would look like:

when HTTP_REQUEST {
  HTTP::redirect "http://x.x.x.x/receiver/ups"
}

Note that I used "x.x.x.x"...this would be a redirect back to the hostname or IP of the Virtual in question. This would, however, hit a different VIP, since it would come in on port 80, rather than port 443.

So, you'd have to VIPs set up with the same IP, one on port 443, with the above rule applied, and one on port 80, without the above rule.

The second VIP would have your pool as a resource, and traffic would be passed to the servers with the modified URI.

The other option would be to terminate SSL on the BIG-IP, and modify the URI before the request was sent to the server, and re-write it on the way to the client, but that's more involved. If having a redirect in place is an acceptable solution, it's much simpler.

HTH,

Colin