Client certificate-based authentication from 1IM to web-service

We have an existing integration with a target system via a web-service API. For that, 1IM performs calls to the web service API from a custom script (in DialogScript table) which user auto-generated proxy-code script (in DialogWebService table). These scripts use WCF technology and BasicHttpBinding.

The target system service provider now requires us to move to using certificate-based client authentication over https.

We don’t see any option to specify the client certificate via 1IM UI wizard that auto-generates the proxy-code (Designer app -> Base data -> Web services -> Integrate the new service) nor in the 1IM documentation (currently using 8.1).

Does anyone know whether 1IM version 8.1 does support certificate-based client authentication on proxy-code generation from the web service integration wizard UI?
If so, where can we specify it?
If not, do later 1IM versions support it?
If not, is there any recommended approach or work-around for how could we implement certificate-based client authentication in our current version of 1IM (8.1).