Over the winter I tried a lot of different combinations which would allow me to have some versatility when it came to carrying my gear, both at air shows and at the various exercises that I attend every year.
I carry two 7D's, one armed with the 100-400mm lens and the other with the 18-135mm lens.
My gear of choice is the Think Tank Digital Holster 20 for each of them, and those are mounted on a Steroid Speed Belt coupled with a Pixel Racing Harness. Also attached is a water bottle holder, which goes on the back of the belt.
I also wear a fishing vest (can always use it for more than just fishing!) where I keep a couple of extra batteries, a couple of filters, my CF card carrier (room for 8 CF Cards in there), and a couple of snacks and my wallet and/or passport.
In a recent trip to Florida I really enjoyed the system, and feel that it meets my needs when it comes to what I'm looking for as far as gear carrying goes.