[stunnel-users] using a socks5 with user/name authentication

Hello, I have a vpn service that provides a socks5 proxy using user/pass authentication. Using stunnel would allow me to use the service with other clients that allow for a socks5 proxy but normally no authentication. Could anybody tell me 1) is what I'd like feasible ? 2)How do I provide user/pass to the configuration file ? Your help would be very appreciated ! alberto