Strange, the sky2 module is located in the initramfs of the media directors (release 41 at least) and is manually modprobed by the initscript from there.
If you card works with the sky2 module from 188.8.131.52, then it should also work with pluto.
At what stage do you get the error ? Does the detection of the laptop works (first network boot) and fail after trying to boot as an MD (starting from second network boot), or it fails starting the first time ?
If it fail at the first network boot, try using this howto: http://plutohome.com/wiki/index.php/Generic_PC
to get it recognized by pluto then try to boot it again.