This site contains a patch that updates XS-1 to the latest beta version. 
The patch only works on the latest VSTi version, currently R6.

Instructions:
 - download the xdelta.exe patching tool and place it in the windows folder or somewhere else in the path
 - download xs1beta_patch.zip to the folder with "Jeskola XS-1.dll"
 - run patch.bat

If the patch works, you'll have a new file called "Jeskola XS-1 Beta.dll". 
The original file is not modified. See changelog.txt for list of changes.

There's no support for the beta version, but if find bugs please let me know.