I have a nylon MLD SS, and it has not worked out well in a situation similar to what you described (rain/wind blowing in through the opening of a A-framed tarp). Unless you pitch the tarp high, there is not enough upward pull on the door of the SS to keep it very taught; it just billows and the rain gets around the edges of the fabric door (through the netting).
I got lucky, as the thunder storm only lasted about 20-30 minutes. Had it have been an all nighter, I would have had to pack up and re-pitch the tarp another direction.
I have switched to a beaked tarp (MYOG), and hope to make a cuben version of the SS with catnary seams all over (hope that helps with the tension issue).