Thanks! I was worried about it too. I added 140lbs of lead to the end of the z tube to help with resonances work pretty well. The z is really heavy and the steel is 1/4 inch thick so it is pretty burly. I can take a 3/4 cut out of mdf with a 1/2 by 2" carbide router bit at 300+ ipm. The z its self is really pretty rigid.
Chad