ETers, Let's say my account has $25,000 in cash which means I have $100,000 in buying power (4 x 25k). I decide to buy 500 shares of an ETF at $140/share and it cost me $70k (so now my buying power is reduced to $30,000). Now that I am long this ETF, can I reverse the position (get short 500 shares) by selling 1,000 shares? I guess I am concerned that IB would not let me do this due to insufficient margin (or buying power). After establishing the long position, I would only have 30k in buying power left. If the above would not work, what about sending 2 sell orders simultaneously for 500 shares each? The first order would flatten my position in the ETF and the second sell order would establish the new short position. Would this work? Any thoughts or suggestions would be very helpful. Thanks!