Quote from stevesbg:
May not matter to YOU but for my uses, I want to know how they handle problem days (exchanges down because of problems, natural disasters, outages, etc) what is their plan for answering the many phone calls they would get from customers trying to get out? How many dedicated lines do they have in place?
As Oldtrader tried to point out, margin is set by the exchange. Mirus may have some arrangement but overnight is not negotiable (I realize the OP doesn't keep em overnight/I do).
Let me put it this way, if there's a choice between two brokers, one who has a good plan in place for emergencies and one who simply lets the phone ring, I'll pay a bit more for the better prepared broker. It only takes ONE event (remember you can lose more than your account if a trade goes the wrong way) to take you out of the game and out of your life savings if it goes badly wrong.....
Good luck