Im 5'11, and I use a sumo stance.. I try to dead with a shoulder width stance, but my knees do this weird buckle ing thing towards the top of the motion.. like they butterfly out slightly right before I reach the top.

5'10", and use a shoulder width stance. Here is a pic to show you how I do my DL.

6' I use shoulder width. If your knees are buckling out ward at the top of the lift try pointing your toes our slightly.

I use shoulder width on deads when performing this exercise as well.Saturn what does pointing your toes outward do to correct Buddys problem?I remember when I started doing deads in my younger years that I was loading the bar way to heavy, and it was compromising my form.Hence the knees buckling .Work on your form first and formost then load up the bar bro.
I,m not questioning your statement Saturn ,I would like to know for myself if it could help me pull more weight when I plan my next bulking cycle come fall .

shoulder width with deads also. i feel sumo puts to much strain on the lower back