ThanX brother!!!! Well, on the preachers I dont cheat the movement any. Sometimes I lower the bar about 3/4's as not to stress the elbows too much.
But when I do standing EZ bar curls Ill use some swinging to get extra reps, or if Im going over 200lbs Ill use some swinging from the onset! I dont even weight 200, so the weight would throw me off balance if I didnt. My form can get a little nasty on some of the heavy sets, but I try to control the negatives slowly. I make sure I am beating the shit out of my arms however. ThanX again!!