say nun are you sure about this set up personally i would not trust it, those frame are made soley for racing. i reckon your putting way to much stress and weight on that beauty.using 28 on the rear wont help if god forbid you put the out a couple on mill Your walking not enough clearence on the stayes.
but listen i'm probable been just to careful if it works fair play to you for at least giving it a go but if your left on your ass in the middle of the road (Frame failure) you have been warned.