After reading Daniella's thread, I've made some modifications of my own to my LowePro MicroTrekker 200 bag, so I thought I'd share:
Excuse the bad pictures, but they were taken with my Pentax Optio 33L POS, which sucks for close up stuff half the time.
Here is the bag done up - notice the extra strap just visible under the front flap (and also the fact I have removed the LowePro label):
http://www.picturepunk.com/photos/bag1.jpg
Here you can see the strap I added more clearly:
http://www.picturepunk.com/photos/bag2.jpg
From the side, you can see where I attached the strap - on the lip, just to the outside of the zip (so on the main back of the bag essentially):
http://www.picturepunk.com/photos/bag3.jpg
Inside, I have used one of the velcro flaps to cover over the lens / body section on my camera, to firmly hold it in place (in the pic, my camera has the 17-85IS attached. The hood you see is my 70-200F4/L hood just nestled in below the end of the 17-85IS). The 17-85IS has its hood on reversed, but its all hidden by the velcro flap:
http://www.picturepunk.com/photos/bag4.jpg
here is a shot with the strap clipped across, just so you can see the level that it runs at - right at the point where the lens joins the camera - to make sure that the camera cannot fall over the top (obviously in normal use the front flap would be up, with the strap fastened over that!):
http://www.picturepunk.com/photos/bag5.jpg
And lastly, because my 300D has a battery grip attached, I have placed one of the velcro flaps below the lens, about 2 inches up from the back of the bag, to help support everything, as the bottom of the camera body is not flush with the bottom of the lens, as the battery grip is attached:
http://www.picturepunk.com/photos/bag6.jpg
Overall I am pretty happy now I think. This bag holds all my gear (300D, 17-85IS, 70-200F4/L, 50mm 18.8ii), plus hoods, cards, and all the other assorted gear I need. I also think that the chance of anything falling out now if the zip was to fail is pretty small. Also, by adding a horizontal strap, it will hopefully keep the whole front flap in place if the zip fails, which means that my lens to the sides will not fall out either.
