Currently (as of Revit 2014), it is not possible to assign a vertical justification, set a fixed row height, or perform several other basic formatting techniques to Revit's Schedules.
Thank you for your post. In this case you can leverage the development product feedback link (listed below) to communicate the need for such enhancement sin future release. This is a direct link, and gives our end users an opportunity to express the business impact and opportunity with these enhancements directly to the development team for further consideration.
Development Product Feedback: http://usa.autodesk.com/adsk/servlet/index?siteID=
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