I added a method to do this and sent a pull request to AndroidAsync on which Ion is dependent:
https://github.com/koush/AndroidAsync/pull/34
It's merged now so a simple call to setHostnameVerifier(HotstnameVerifier ver)
will do the trick! Example:
Ion.getDefault(context).getHttpClient().getSSLSocketMiddleware().setHostnameVerifier(myHostnameVerifier);