i use a 3/32 drill bit make a hole in the center of the screw head (not all the way through like 1/4 of the way) then I use a ez-out bit and remove the screw. Dont know if you know what an ez-out is but it works on a backward thread principal. As you turn the bit left the loosen the screw the bit dig its way into the screw tighter and tighter untill the screw breaks free. There pritty cheep and you can get them in any auto parts store, or sears, for a couple of bucks ..... I never like to use a dremel cause if ya like me you run the risk of marking up the chassis
Hope that helps. Good luck!!!!