I have a Yakima Rocketbox 11. Takes up half the roof. Worked well on the Fozzy, and works well on the Prius. 22x14x89. I have thought about getting a full width box, but with one kid, we haven't run out of room in this one.
I think a Yakima Skybox 21 fits your requirements. Roof boxes are damn expensive, but worth every penny for vacations with family. The moment you have everything you need and can still see out of the back window is priceless.
If you already have stuff from Yakima or Thule stick with one brand. Then you can order the lock cylinder kits and do 1 key for all of em.
I think a Yakima Skybox 21 fits your requirements. Roof boxes are damn expensive, but worth every penny for vacations with family. The moment you have everything you need and can still see out of the back window is priceless.
If you already have stuff from Yakima or Thule stick with one brand. Then you can order the lock cylinder kits and do 1 key for all of em.

