I am a strong supporter of the "feet up" position, as this is the way we were taught back in 1994 during the A320 type rating. Since then I kept teaching it this way to my trainees and that was also the policy in the airline where I have spent the most of my career. I believe that the "feet up" position has only pros and only 1 single con that I have had the chance to experience a few times on some trainees, that it is the possibility of applying brake pressure during take offs with strong cross winds on the upwind brake, especially if the trainee pumps the rudder. That happened maybe 3 or 4 times in 25 years so I am happy with that statistics compared to all the benefits of the feet up position.