How to install .tar.xz file using automated plug-in installer

Hi,

I am trying to install littleutils-1.0.32.tar.xz, which is an additional plug-in required for CW Image Optimiser. The plug-in assists the CW Optimiser plugin with png, jpg and gif optimisation.

I downloaded the littleutils-1.0.32.tar.xz from the official Source Forge page that was given when installing CW Image Optimiser, so I know that it is safe.

However, when I try using the automated plug-in installer built in to WP, it will fail and issue to error message:

The package could not be installed. PCLZIP_ERR_BAD_FORMAT (-10) : Unable to find End of Central Dir Record signature

Any help with this would be appreciated.