Hi:
I may be wrong, but, what you are trying to do is...:
http downloader --> provide domain name (ssl) -> connect to stunnel -> download files
You can't provide an IP to the http downloader but you can provide an alias (aka domain name).
Then, when you need to download files through ssl (https), just provide a name configured in hosts file that resolves to local IP or the IP managed by stunnel in that machine (localhost, for example) to the http downloader.
Then, just edit the conf file to change the connect parameters (domain name to connect to) for the service you pretend to use inside stunnel and reload the conf file.
This results in:
http downloader --> name in hosts file pointing to IP used by stunnel --> connect to stunnel transparently --> stunnel brings ssl tunnel (sorry the obvious) to http downloader to download files.
Shouldn't be problems to provide full url to the http downloader.
Easier way? I don't kow. Maybe others can help. I don't know if there is a way to automate the change and reload of the conf file.
Regards.