I am still in the planning stages, but I figure that I would be carrying no more than 15 lbs in front panniers. I am planning on a total gear load of 40 lbs. I have seen some racks with a platform on the top with the ability to carry the panniers either high or low. The additional flexibility of the platform is appealing to me.

I am am more concerned with mounting. Is there anything out there that mounts with the existing lugs on a Trek 520? I have seen some that mount on the brake bolts, but I worry about vibration and other stress on my brakes.