I'm wanting to replace the bolts used to hold my cantilever brakes on as they've rusted and look pretty terrible on an otherwise clean bike. Is it ok to use stainless (A2-70 or A4-70) for these or would I be better with mild steel and replacement more often? 
I'm less concerned about the rear as the braking force pushes the calipers into the frame, but if a bolt head breaks off on the front under braking it would turn fairly ugly.