Nice little article on SSIS buffering:
http://intelligentsql.wordpress.com/2013/06/25/ssis-performance-tuning-max-default-buffer-rows/
Check out these system sprocs to get info on query row size:
sys.dm_exec_describe_first_result_set (http://msdn.microsoft.com/en-us/library/ff878258.aspx)
sys. sp_describe_first_result_set (http://msdn.microsoft.com/en-us/library/ff878602.aspx)
You can also get query row size with the estimated execution plan in SSMS.
Lots of tweaks for SSIS!
