Just thought i should share this, i was digging up my storage when i found my old camera bag, its a Crumpler karachi outpost, i customized it for my phantom 3 pro and it fits perfect with lots of room. check out the pictures below.

It fits the phantom3, rc, 2 batteries, wires, charger and props and i can fit a 17inch macbook pro, ipad mini and sunshade in the laptop sleeve as well. And there is still alot more space depending on how i customized. The backpack is also very well built with lots of padding.It is compact, great for hiking, carry on, travel- you could bring your p3 anywhere with this.
I DIYed the kaizen foam i got from fastcap. I normally have to remove the rc first, slide the phantom 3 forward slightly before removing it. I dont think its a issue since the motors sit right underneath the padding. The backpack is deep, so if you put the p3 in the middle, it would close as well.

The only problem is Crumpler has discontinued this model, so it will be difficult to find. I saw a couple on ebay going for $60-100, it use to retail around $300-400

vu.q.le@outlook Posted at 2015-6-30 02:27
This is an ugly backpack and the reduced price reflects that. There is no way this backpack is worth ...

haha yep, but its really compact and works very well.
IMO the design is streamline, it doesn't seem like you are carrying a big box on your back as with most of the other p3 backpacks out there.

I use an Vanguard Up-Rise II 48 Backpack for my P3P and accessoires. Great quality camera backpack, very useful for travelling and enough room to fit other gear in aswell.

Here is a video review