If your knees are much higher than your waist, it starts stretching your lower back and you have to use your abs more to keep your balance, when you start to draw, your torso muscles are already stressed so you are really straining, so you hunch over to take the stress off your abs, which puts your eye at a different angle...do you began to see the problem? Easy fix, get a different chair or practice from the short seat. Your muscles will build up if you practice regularly and you will get the organic computer recalibrated for the different angle. Bill