Dan, I really like the exchange-supported implied spread markets for anything they are offered in. The legging risk contains slippage variables that can defeat the entire purpose of spread trading as a strategy.
The 'challenge' with trading outrights based upon spread correlations - which is a very powerful edge into and unto itself, is that factors unrelated to the spread correlation come into play and can leave a mark. For example, you may correctly believe that the NoB is weak for example, and you may be successful shorting the ten year notes and taking a tic here or a tic there out of it, but if the ES starts to tank or gaps down your short note position will indeed leave a big mark.
The 'challenge' with trading outrights based upon spread correlations - which is a very powerful edge into and unto itself, is that factors unrelated to the spread correlation come into play and can leave a mark. For example, you may correctly believe that the NoB is weak for example, and you may be successful shorting the ten year notes and taking a tic here or a tic there out of it, but if the ES starts to tank or gaps down your short note position will indeed leave a big mark.