FWIW, the Flipside 200 or Flipside Sport 10L are about the same size and slightly smaller than the Sport 15L. If you don't have more dividers you can always email Lowepro and they might send you some extra that will allow you to make it fit your stuff better. I have the 15L with 4 dividers in addition to the center one and have it sized for my 50d and small (100mm non-L macro is my biggest) lenses. If you want, I can post a photo of the 200 vs 10L vs 15L.
The tripod holder on the Flipside Sport models is fantastic in my experience and one of the reasons to keep using it over the regular Flipside models.
It won't let me post on this thread again, so here are the photos:
Left to Right: Sport 15L --> Sport 10L ---> 200
Left to Right: Sport 15L --> Sport 10L ---> 200
Left to Right: Sport 15L --> Sport 10L ---> 200
Flipside 200:
Flipside Sport 10L:
Flipside Sport 15L: