huh, beat me to it...

deflection of a fixed-fixed beam with a central point load (worst case) is:

d = P (l^3)/(192 E I) = 250 (500^3)/(192 * 2e5 * pi/4 * 12.5^4) = .042mm

Ross - sanity check - radius is 12.5 not 25 - they were 25mm beams.