Clarification of bankroll requirements and moving up

I'm going to refine my definitions of "required bankroll" and outline my rules for taking shots at the next level. For ease in calculation, all my goals are based on rigidly playing a single level until I hit 500 BB's for the next level, then exclusively playing the next level. There are two things wrong with this.

1) It's not practical. Moving between limits should be a more fluid situation. If playing three tables, I should mix in one of the new limit over time, then two, then be playing all three.

2) It's probably too conservative.

In reality, when I am moving up I should have 500 BB's for the next level down to fall back on. So once I hit 500 BB's for .50/1.00, for instance, I am comfortable mixing in some 1/2 games since if it goes really badly, I'll still have $500 to fall back on to play .50/1. Then it will be until I'm over $1k that I would start mixing in 2/4 games. So the $600 - $800 range will essentially be a transition from .5/1 to 1/2 where I'll be playing both limits concurrently, depending on game selection and just how I feel. Once I'm in the $800 - $1200 range I figure I'll be playing pretty much 1/2 exclusively, and at the top end of that start mixing in 2/4 games. All the while adjusting up or down depending on how I'm running, what the bankroll is, and how comfortable I feel about the limits.

So right now with just over $400 in the roll, with plans to deposit more, I'm starting to mix in 1/2 just to see how it goes.