I am thinking it's a good idea to put inside normal backpack.

The patented Padded Insert System.
The heart of a Domke Shooter’s Bag:
Another Domke exclusive, the Padded Insert System organizes and protects your gear with less fuss... and a lot less bulk. Interchangeable, compartmentalized inserts let you custom-tailor your Domke bag to suit any application or equipment combination. And unlike the flat walls, hatches, floors and bridges you find in other bags, these inserts are complete, self-contained storage components. Which means you can move — or remove — any Domke insert without having to empty it first!