I think so, but even with an A in Calculus I have trouble with this.
I am confident that you are correct in that converting in December of year 1 and withdrawing in January of year 5 meets IRS rules for the 5 year period.
The way I figure how much is needed:
Suppose you spend $40K per year and start with $160K in your pipeline.
Convert the $40K in December of year 1 that you want to spend in January of year 5.
One month later, withdraw $40K in January of year 2. Pipeline down to $120K.
One year later, withdraw $40K in January of year 3. Pipeline down to $80K.
One year later, withdraw $40K in January of year 4. Pipeline down to $40K.
One year later, withdraw the $40K in January of year 5. This is the $40K you converted in December of year 1.
Given the above analysis, it looks like you could even be as low as 3x annual expenses for the majority of the year (January through December) and only be up to 4x annual expenses for a few weeks around the end of the year (December through January). But that somehow doesn't seem right. Oh well, I'm sure someone will be along to correct me if I am mistaken.