I did it and dropped 2 5/16 hex heads while working the underside of the Playfield with the Playfield upright. It took me 5 minutes EACH to find them even knowing within 10" where they were.
I bought these http://www.mcmelectronics.com/product/22-11125?green=CD39ABEC-F86B-5770-AD70-BB323DEE6BE0
They seem to be well made but the hex head screw will fall out before I get the driver to horizontal.
If these cannot be magnetized I am gonna buy something like these http://www.amazon.com/Klein-Tools-646M-Magnetic-Cushion-Grip/dp/B000936QV0/ref=pd_cp_hi_0#productDetails