Keep the bar against torso throughout movement , your elbows will be pulled back behind your body.You are basicly draging the bar up your body hence the name drag curl
I can only get the bar to just under the pec line and I think you shouldnt be able to get it any higher but the contraction is intense hold it for a couple of seconds and really squeeze hard , you wont be able to use alot of weight with it but as ursus said a great finisher especialy if you wait 30 secs between sets.