That 25g tarp is really interesting. Combined with a MLD event bivy, total weight would be about 12.5oz. Add some bug netting to hang down from the edge of the tarp, probably around 13oz. Not bad, IMO. Very easy setup too.

There are plans to make that tarp at
http://www.backpacking-lite.co.uk/diy/make-an-ultralight-solo-micro-tarp.html