The I3 fits in a Lowpro I2 backpack
It fits pretty good. Someone mentioned to place it in travel mode. But placing it in landing mode works, like it was designed for the I2, much better. This way there is no stress on the lower booms.
You can place the X9 camera, lenses and 6 sets of batteries in the storage compartment. Props fit the dedicated place also perfectly. The motor protection covers also fit perfectly.
There is even some place for WB37, filters, snacks etc. if you want to strech it out. The rc's need to go to the backpack of the cam operator as they will not find any place in the back pack. So you might as well place some of the batteries in the backpack of the cam op to reduce a bit of weight

Man I'd love this backpack... if anyone has an extra I'll buy!