Too many variables
But that's not all...
I also try to take into consideration different chair heights, heel height, and on occasion even trouser material! My goal as a teacher is to get my students to be as comfortable as possible with real-world cello situations, so I must include these realistic (and sometimes not ideal) variations. Not all of us are able to take a custom cello-chair with us wherever we play (the most I can get away with for most concerts is a subtle seat cushion addition!).
Your comfort is key
Keep in mind that you must fit the cello to you. Not the other way around!
Head, shoulders, knees and toes
I would love to hear your thoughts on sitting with the cello. Do any of you use Posture Pegs?