You may be a beginner, but this is not really a beginner question. I'm guessing from the 100-400 that you have Canon gear - I would suggest a post on one of the Canon forums. You're much more likely to get useful response there..
Unfortunately I can't help, as my gear does fit in my backpack (five lenses but they are somewhat smaller than yours!) and I have no experience of rain forests ..
I dont have what you have but someday I will.And on that day this is what I will do..
Ill have a small strap bag over my shoulder with one cam one lens. to grab the quick shots..
And either on my back a big back pack for the rest of the equipment.Or ill get one of the hard cases to put the rest of the gear in..
Everything as to be watertight, in case I must swim across a lake/river....Or if it starts to down pour for hours..
That way my gear will be safe...
On day hikes with too much gear, aside from the pack (LowePro Rover) I'd have a toploader bag for the chance encounter while in transit. After the pack is mounted, one can sling that diagonally across the shoulders, or obtain a toploader chest harness..
LowePro has a new pack that they contend allows one to pull out the camera from the bottom corner of the bag. I find it interesting, but I'm skpetical as to how easy..http://www.lowepro.com/Products/Backpacks/allWeather/Primus_AW.aspx.
You'll have to ignore the gallery's collection of bad compositions, improper exposures, and amateurish post processing. .
Image control:Zoom outZoom 100%Zoom inExpand AllOpen in new window..
An awful lot depends on whether you will be hiking with all the equipment all the time..
You want to take a look at this article:http://www.luminous-landscape.com/locations/costa-rica-2003.shtml.
Problems occur with non 1-series camera or non L-lenses one sealed bodies. The Canon 100 mm f/2.8 macro lens, for example, is extremely well built, but not environmentally sealed. The 180 mm f/3.5 is an L lens, but it is much heavier and larger to carry..
I'm just trying to get a feel for what others do. I don't expect to carry everything around with me everywhere I go. Even with less to carry around I've found myself fumbling at times and have thought "there's got to be a better way"...
Get yourself a good belt system (LowePro, Thinktank, kinesis) and get two pouches to hold your two cameras and the most commonly used lenses. Then carry the rest in a smaller backpack..
Or, use a backpack combined with a Newswear Chestvest, although this will make you feel like you are wearing a suit of armour..
The closer you can get to having the equipment move as you do, the better, and if it's more evenly dispersed over your body, it's less of a heft..
Personally though, I'd go lighter. One flash, two bodies, three lenses max. This will still feel like you are carrying round a kitchen stove, but less like you are carrying the whole kitchen..
This guy seems to have it taped for traveling 'light':http://www.karlgrobl.com/EquipmentReviews/index.htm#ReviewTopYou name it, I've broken it...
There has been a time or two that I needed to use my wife's head (with hat on) or a shoulder to steady the camera. But seriously, I wouldn't consider taking an expensive trip without a tripod. That's why I asked. Make sure to use pipe insulation on the legs and a strap so it can be slung over a shoulder to make it comfortable to carry.Larry Bermanhttp://BermanGraphics.com..