Well the only reference I can find is this from the project.py file, but im not sure where to increase the size or where is the "osv" from where is importing fields.

from osv import fields, osvclass project_task_work(osv.osv):
_inherit = 'project.task.work'
_columns = {
            'name': fields.text('Work summary'),  
            } project_task_work()

Thanks!