Ewww, ubuntu ...
Linux doesn't take that much ram, but still anything above 128mb is really nothing when you run something like Gnome (eww) or KDE ... Your minimum config here is only for console mode. Gnome likes RAM, so does KDE.
I hope you are going to get away a little of ubuntu, if it's just for skinning it, I don't think you will have any future, get your own repos, own release cycle, own everything.
I won't use it, but still : Good Luck !
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