Converting a non-camera backpack

I would be interested in hearing from anyone who has modified a back pack to carry photographic equipment safely -- safely being the key word. I've wondered whether any company sells, for lack of a better term, inserts that would fit in a back pack. I have a couple of very fine Maxpedition packs that are big enough to carry my equipment and personal items -- jacket, books, lunch, and so forth.

Probably, the easiest thing would be for me to buy a made-for-photographic equipment pack, but still . . . .

I was asking a similar question for my upcoming backpacking trip to Europe & Australia. Domke makes padded inserts that you might find useful. They're meant to drop into their shoulder bags mostly, but I think they would work for a backpack. I'm considering these for my trip.

If you find something that works for you, please post your setup for the rest of us!