re: My largest bowl so far

I doubt that wood movement will be an issue.  The rule of thumb is that under about 12" it won't matter and since the vertical pieces probably only add up to about 8" combined, they won't have much affect, especially since they are spread out.  There could be more of an issue with the bottom moving across the grain but given its diameter, I don't think it will be a problem either.  
My 2 cents.