OK, forget the GG Mariposa idea. My grandson (9) carried the Mariposa and his sister (7) carried the butchered (by me) REI Comet (no relation whatsoever to the Six Moon Designs Comet) into Shi-Shi Beach at the extreme NW corner of WA. Thanks partly to the heavier pack, Sissy carried almost 2 lbs. more than JP, but was far, far more comfortable. Their dad and I are going to look for an Osprey or Deuter pack for JP. We might butcher that pack too, or at least remove the lid, to cut the weight a little. But it's very obvious that a well-fitted frame and, above all, load lifters to keep the shoulder straps from pressing down on the shoulders make all the difference in comfort for a young child!!