Questions about WS55511

I am in the process of replacing the convergence chip and noticed the chip is only secured to the heatsink by a clamp. Do you think it would be okay to drill two holes and screw the chip to the heatsink? I'm not sure the clamp puts enough pressure on the chip to give good heat transfer. I would also like to know what is the best way to clean the lamps? They have about five years of dust on them. Thanks for any help you can give.