The past few years we've used a lot of rivets, mostly on the mechanism, but our 2008 chassis was riveted together (fiberglass channel and sheet aluminum). We prefer smaller rivets, mostly 5/32", we also use some 1/16" and 3/16" rivets where appropriate. Sometimes the rivets get loose...that generally means the joint was not designed properly.
See if you can find pictures of some past 1501 robots
