I think I know what you are trying to achieve, I'm not on a windows machine at the moment so cannot post any screenshots but I will try my best to talk you through it and post screenshots tomorrow if I can.
Option 1 - Single Miner
1) Fill out the host page as you normally would to connect to your RPi
2) In the left hand navigation pane select "SSH >Tunnels
3) In source port fill out 8080
4) Destination Port enter antIP:80 example 192.168.1.99:80
5) Click the add button
6) Go back to your first page and connect to your RPi
7) Log in to your SSH session and ensure you can see the # or $ shell
On your web browser navigate to
http://localhost:8080This will direct that web request through the SSH tunnel to your Antminer.
Option 2 - Multiple Miners Chrome and Foxy Proxy
1) Navigate to "SSH > Tunnels" in Putty
2) Select the Dynamic radio button
3) Enter 8080 in the source port
4) Connect this session to your RPi as normal
5) Ensure you have the # or $ prompt.
6) Configure Foxy Proxy to use localhost:8080 as the proxy server and to direct all traffic towards the proxy.
7) Navigate to your miners IP as you normally would
NOTE: Please be careful about using this method on a corporate network as this can be used to circumvent certain web filters which will more than likely be against your IT Policy.
EDIT: Didn't read post #3, ignore the above as this will give you remote access to your miners via the RPi as an SSH/Proxy server it will not tunnel the connections towards slush pool through an ssh connection.