My camelbak mule is pretty big. Only worn mt biking. Vented back areas, wide waist belt, padded shoulder straps and can adjust the width of those as well. I find a rack and bag so much easier on the commute. Think about 10 lbs up high or below the seat for center of balance. Plus less sweat and backache. One more thought. I have a frame bag on the Karate monkey. Works well, can still fit water bottles in the main triangle, easy access below the top tube.