Flipside 400 looks like a nice size, but does that waist belt come off? there's one on my expedition and its padded nicely, however that's what makes a lot of the bulk.
Bobn15, have a look at the Streetwalker Pro and the Flipside 400 (upgrade in size, padding and comfort over the Flipside 300). I actually ordered the Flipside 400 yesterday. Chose it over the Streetwalker Pro as it has better internal padding, larger outside pocket and a little more space inside.
The smaller Streetwalker is not designed for a gripped or Pro series camera.