Which version of Widevine are we supposed to use with Slimjet?

[TryKindness]

I've tried many different dll version combinations and Widevine usually installs fine, and websites that require Widevine recognize that it is installed, but the content still doesn't play.
When testing Widevine using bitmovin (https://bitmovin.com/demos/drm), I get the following error message:

DRM: Unable to instantiate a key system supporting the required combinations

As I understand it, this is related one (or both) of the Widevine dll files being of the wrong version.
Can you please let us know which dll versions work with Slimjet?

Thank you!

OS: Windows XP Pro
Slimjet: 10.0.13.0 (50.0.2661.75)

The dll versions that I've had the most luck with in other chrome-based browsers in XP are:
widevinecdm.dll 1.4.8.903
widevinecdmadapter.dll 49.0.2623.110