I made a throw recently that is 50x70 and I, at 5'8" find it too short. I like to snuggle right up in my quilt, turning myself into a human burrito, wrapping around and under my feet...My husband is the same way.
So if *I* were 6'5", I'd want it at least 80". Heck, I'm making a new one for myself and I'm making it longer than 80"...of course, it's hardly a throw anymore at that size... :lol: but it sure would be cozy!