Well I survived the night, although it wasn't originally forecast to rain, it rained fairly heavily from about 3 in the morning. Fortunately I slept at the back and it wasn't too windy so no rain reached the back and if it had I was in a bivy bag anyway. When I seam sealed the trailstar earlier, I followed the instructions in the link Mat supplied and thinned the silnet down in the following ratio 3:1 white spirit to silnet before applying. I have to say it worked very well and no leaks were found, I really love the space and the versatility of pitching options with the trailstar.
To anyone thinking of getting one, all I can say is do it, you won't regret it!