The cello fits you, you don't fit the cello.
In Glenda's lesson this week, it was looking like her wrist was bent - not a great thing to have in the relaxation/fluidity department, which is what she's been working on this season... (She means business in that practice room of her's!)
In the picture above-left, you'll notice her head/neck are aligned correctly. That's obviously something to aim for, but putting the cello in that position makes it so her left wrist has to bend when she's playing. :-(
When we hiked the cello up a bit, the C-peg was able to get out of the way to allow the cello neck to lie closer to her spinal alignment. This change did two things. 1) It allowed her wrist to straighten out. (Yay!) 2) It made her head tilt to the side to avoid the C-peg. (not yay.) This is a common problem for cellists (myself included) and Glenda is a prime candidate for the Posture Peg.
I'm reminded how fluid and open minded we need to be when playing the cello. There are so many variables due to time, space, skill, emotion, and mental clarity (among many others too!) They all affect something as (sometimes) seemingly simple as holding an instrument.