Both TID 3988333 and Craig's Proxy says you want to use the above parameter in the [Extra Configuration] section to fix 'Malformed CONNECT request sent to back end web server'.

However, this is not a parameter that appears when looking at Proxy Console Screen 63 with the default proxy, so there is no default value for this. In addition if you set this parameter or the 'noDummySlashUpsteam' variant in the [Extra Configration] then reload the proxy and look on screen 63, you still don't see it.

So is this a valid parameter any more?