We are trying to use radius scripted authentication and have it working. We found an issue (well, we think it is an issue) though.
If you log into Splunk with radius scripted authentication and close the web browser (IE) you can re-load the browser at a later time and get back in with no authentication prompts at all.
If the session timeout is set real low, when you log back in it will prompt, but we want our session timeouts to be more than a minute or 2.
We are using the provided radiusScripted.py script with our radius configuration.