I've been trying not to arm bend. I tried using straps to relax the arms, i slowed down my first pull, i tried complex like halt clean dls + cleans, clean pulls + cleans... I tried a lot of things, but none of that made this problem disappear.
The biggest concern I have with this, it's the arms being used as a 'reverse curl' and not going high and outside like an 'upright row'. Last saturday I did cleans from the floor, and in the last repetitions I focused on keeping the hook grip a little longer, and although my arms did bend yet, the pullunder felt very fast and agressive.
Try internally rotating your arms (turn the points of the elbows out to the sides) right from the start and keeping them oriented that way - that will prevent you from pulling the elbows back and will set you up to pull high and out before the turnover (which you will have to do actively). You may still bend a little early to get the bar higher toward your hips, but I wouldn't worry about that.