I don't have that bag, but I do have the flipside 300 which looks like the same size based on Lowepro's descriptions. 2 lenses and two bodies? I would think easily, with some room to spare.
I put a non-gripped 7D with the vI 300 2.8 attached in my Flipside 300 with room for a body and a lens (not attached) or a flash. I didn't even remove the little pouch at the top of the interior which would give me another few inches.
I have the Lowepro Flipside Sport 15L AW and it is more then deep enough to room an EOS-1D X, so a 7D + grip should be fine. I'm not quite sure whether the Sport-edition is another model, than the one you're asking about, but I sure love it!
I have the Flipside 15L, in it is my gripped D700 wearing the Vanguard QS-65GH&14-24mm, and it fits well. Before, I had the gear fitted in my Flipside 300&switched to the Flipside 15L because of the depth - the paint on the top of my D700 was getting rubbed off in the Flipside 300(without the Vanguard QS-65GH, it won't rub against the interior of the Flipside 300). I think you'll be fine.
I have done a "hands on" in to my blog, it's in finnish but the pictures tell a story too. If someone is interested at this bag. You sure can fit with ease a body+battery grip. I have also had a flipside 300 and it's not as deep.
I ended up getting this bag. I used it for the first time shooting a basketball game last night. It worked great, nice and light. This is going to make a good grab and go bag. Looking forward to using it in the Rockies this summer.
