I have a/c with IB and I have bought US shares for the money I have given to them. As margin is 50% of my buys, I have more money in my a/c as "available funds". The question is how much it is wise to use over and above my own money. ? I would welcome comments from others traders as to what they do. In theory I have double the capital at my disposal-0fcourse I have to pay interest on excess use but that is only about 1.5% above market rate. Thanks