no la, the bag can hold very heavy stuff, because i read their information sheet about the bag. this bag had gone thru a test to hold 110kg. truely that is what i read from their notes. so it can carry heavy things, but of coz not too heavy that will kill your shoulder.
also the large size bag is better because after you pull the straps on the sides, they are far much smaller than u expect, otherwise u can not put much baby stuffs in it....