I believe aerobars have more torque due to their length (something about the distance from the fulcrum... the math teacher should chime in here sometime) the farther away, the more torque you can apply with less force... I would hesitate putting aerobars on carbon drop bars in general... aerobars on alloy drops shouldn't be an issue, because they can withstand more than 4Nm... I have a friend with aerobars on some alloy, over the last few months he has noticed the bars drop a little over time... its about time to adjust them... they are alloy on alloy torqued up to 6Nm... I think it has more to do with his technique and posture though.