Hello I am with IB and I started selling SPX 1000-2000 boxes to borrow money for my other position since the implied interest rate are cheaper than the IB tier 2 interest rate. I have risk based margin and IB only require a few hundred dollars for margin. Am I missing something or is it standard for IB customers to finance their position like this? Another question is that to place the box order is it standard to start with a price than slowly increase the price, until a MM bot pick it up? I can see my order in CBOE COB but I am not sure the proper way to do this. How about the usual price for this position? I can't seem to find time and sale history of the complex orders. Is somewhere about 2.1% implied interest for 3 month box a good price?