Well, I went to the store with the equipment I talked about, and I was able to fit it in the bag, so I bought it.
If I want to keep it slim I put the 5D with the 17-40L mounted on one side, a divider in between and the 85/1.8 with hood reversed below and 50/1.4 with hood on top. It's a little tight, and you have to be a bit careful when taking stuff out, but I think it will work.
I can fit the 430EX (without it's pouch) and the hood for the 17-40L in the front pockets, however, then the bag is far from "slim" 
Thanks for the input! 
Thanks for the tip, I have to look into that.