I think you want to ramp up your CNS without inducing muscle fatigue. Jumps of 40-50 lbs are probably fine to start, but as you get closer to your max you will want to reduce the gaps of the weight jumps. You want to get your nervous system primed to fire all out, and I don't think you can do that with 50 lbs less than what you want to attempt for your 1RM.
I can't find the link, but there was an article I read on T-Nation about how to 'trick' your CNS into being ready to lift a heavier weight. Before attempting your 1RM, overload the bar with 5-10% more of the weight you are going to attempt to squat/ bench. Unrack the weight and just stand still/ hold the bar at lockout for ~5-10 seconds. Rack the weight and take your 2 min of rest and then attempt your 1RM weight. That method gets the CNS ready to fire on all cylinders and the weight will 'feel light' in comparison to the overloaded bar.
CT also gave a sample ramp up scheme in my thread last week about the layer system 2RM that might help you plan your 1RM scheme: