Ok, here's what I did. I bought some Velcro strips and put 2 on the inside going long ways on both sides, one high and one low. I did the same on the side of the bag. I used Inserts from a previous bag and a bag I got from a yard sale for $1. Lots on inserts in it. I was going to make my own from Styrofoam, which I see no reason it wouldn't work, if you don't mind sewing some covers for them.
Aniwho, here's Pics! I love this bag and it's my daily bag now. As you can see it has a lot of pockets. I have the normal things listed in my other bag reviews in here. The empty space with only the hood is to show where my 70-200 goes when gets back from being repaired.
Lenspens, pens, wireless remote, AA and CR2 batteries memory cards, hurricane blower all fit in these pockets. Filter wallet is in slot in front of the main compartment.
This little area is where you can expand the bag, by unzipping all the way around the bottom gets bigger. I use it for spare batteries.
The slot back there is for my laptop which can fit. I use it though for flat items like my tripod/monopod plates and the twin caps.