Hi
I need to use this fixture(please see attached picture) for machining some cylindrical Aluminum part by my CNC lathe machine
the biggest diameter of plate is near 500 Milimeter with 20 mm thickness and clamped it by the second cylinder on a 3 jaw spindle so it is heavy and maybe need to reduce weight but i don't know does punch and drilling or create some uniform pattern on the back of plate can reduce the vibration during the machining or not ? Instead of Material please let me know what other method can help me to reduce and damping the vibration of machining on the fixture?

Thank you for your time and help.