dts--
Have had V* since mid-november, and can remember only about 2 instances when signal was lost due to weather.  The 18" dish is more susceptible to this than a larger dish would be.  The bigger the dish, the more signal gathering power it has.  When I purchased and installed my own D* system, I went with the larger eliptical dish, and never once had a signal loss in approx. the 2 years I had it before switching to V*.  Will stay with the 18" dish for now and see how it performs over the long haul.  Good luck with your install tomorrow, and happy Vooming!