There is another guy on these boards you have probably heard of... Nick B. He knows a great deal about poly strings - plays with them and strings with them. I checked out his site the other day and noticed he uses a machine with a "traditional" rotational gripper (not like the modified rotational gripper on the Aria). I know he strings poly all the time for himself and his customers, and I have never read of any instances where his machine has caused problems.
If you want to reach out to him directly, check out his site - www.nickbondtennis.com