Interesting article. I am a currency trader and I would say the main practical difficulty in carry trading is that unless you work for a bank you are not likely get anywhere close to the true interest rate of either currency due to the spread on the overnight interest rates. You can see this if you look at websites like forexop.com, where they have done the fee calculations for a group of brokers. This was not a problem back when we had Australian dollar interest rates at 5%, but now with lower rates the spread becomes an issue and adds to the risk of the carry. btw I agree with you about the futures market, which is a better choice for the carry trader who has enough capital.