@bsawlor
Try using our software Robotiq user interface you can found here to manually control the gripper position, speed, and force. You will then be able to see the gripper speed at the maximum setting of 255. Visually, the fingertip speed must be around 110 mm/s at maximum speed. If it's not the case, contact us at support@robotiq.com.
I've got a customer who is working on setting up their gripper(s) and is wanting to push the speed. Unfortunately the activate scripts that are being referenced in the program, potentially are limiting the ability to bump the speed. Looking at sections 4.3-4.5 in the manual indicate the bytes that need to be altered, but once set, what would the speed actually be? It seems it could be slower then expected.