11 reps, nice work, and you weigh something like 90 kg? im
around 85 and can only do 6 -7 on a good day.
I heard that pistol squats are mainly for explosive leg power, so
is it best to do them at the speed as shown in the video? i tend to
do mine more slowly.
damn they are hard too, when i started out, couuldnt even do 1 full
rep, so i did partials and progessviely increase my ROM until i was
able to do a full rep. these definitely work your core too,
something has to keep you from toppling over when your moving up
and down on one leg 
i also think that having a 6 pac is just a gauge of body fat
levels, though those very muscular guys may have somewhat visible 6
pac with high bodyfat levels
