Stainless are fine if you use decent ones, I've had them in the ST2 for ages, the standard ones fitted aren't very high quality, certainly not on a par with Unbrako or similar Hight Tensile screws. Shear forces are not hight enough to cause any problems. Not seen any evidence of corrosion due to dissimilar metals. I've put a lot of stainless bolts on the ST2 as it does see some use in bad weather.
I've never bothered to calculate the shear forces but if the brakes exerted enough force to cause the bolts any grief the front wheel would constantly be locking up wouldn't it
