The Team Drawings in the document section:
http://www.usfirst.org/roboticsprogr....aspx?id=16097, specifically TE-10012.pdf within 2010 Team Field Elements.zip, show a version of the tower using 4X4's as the vertical posts.
If these drawings are official, then it seem the GDC did not intend for robots to attach to the towers using the vertical posts. If they did, then these drawings are invalid for the official game.
Someone need to post a clarifying question in Q&A about this.