Ah, now here's a topic I know something about. Motorcycling with camera gear is what I do for fun. My present motorcycle is a Honda ST1300, and my present camera gear is a Canon 5D and Rebel XT plus some lenses, the essentials being 17-40, 28-135, and 70-300DO. All of the lenses being roughly the same length, and short, makes storage easier.
Since my 700 pound beast rarely leaves the pavement, and then only for shallow gravel or really hard packed dirt, I have a Givi top case that holds my camera gear. The Givi case is an E460, a 46 liter hard plastic case that locks closed and locks to the mount with the same mechanism. Inside the Givi case I keep a CamelBak "Peak Bagger" backpack with 3 liter water bladder (though I don't keep the filled water bladder in the case with the camera gear). Inside the CamelBak backpack I slip the inside padded case I removed from a Quantaray (Ritz store brand) photo backpack.
Finding the room for everything isn't really a problem. Weight is the problem. The padded photo backpack "innards" will hold the 5D with one lens attached, the Rebel XT with one lens attached, both with Really Right Stuff 'L' brackets, and six other lenses. Typically I'll have along the Rebel XT wearing it's EF-S 17-85 lens plus the EF-S 10-22 lens, and the 5D is typically wearing either the 17-40 or the 70-300DO, with the other of those two lenses plus the 28-135 in the bag. If I add anything at all beyond the zooms, the next lens is always the macro: in my case the 100mm USM. Beyond that it's whatever I think I may need: flash or primes. My list of primes is 35 f/2, 50 f/1.4, 85 f/1.8, 100 f/2.8 macro, 135 f/2, and 200 f/2.8 plus Sigma 1.4x and 2x teleconverters (no white lenses yet). I can't carry them all, of course.
You also need to have the other obligitory accessories: CF cards, spare batteries, polarizing filters, hot shoe levels, WhiBal, et cetera ad nauseum. I always weigh my bags to make sure I'm within the weight limit. I don't want $10k worth of camera gear bouncing down a mountainside.
After you get that mastered, there's the tripod. Don't skimp here, you'll regret it. You gotta have one, and on a motorcycle it's got to be especially durable and light, and preferably short, too. My main tripod is a Gitzo 1348 with Really Right Stuff 40mm ball head. My light tripod is a Gitzo 1128 with RRS 25mm ball head. The 1348+40 won't fit into a bag and has to be strapped on, but it's a fantastic tripod. The 1128+25 will fit in my saddle bags or top case (closed length of 21.5 in), but extends high enough that I don't have to stoop much (57.5 in). The 1348+40 weighs 5.8 lb total and is rated to hold 25.4 lb (I subtracted the ball head weight already). The 1128+25 weighs 3.0 lb total and is rated to hold 10.5 lb after subtracting the ball head weight. No camera + lens combination I presently own weighs anywhere near 10.5 lb, so I'm covered with the 1128+25, but the 1348+40 is much more stable so I find myself always strapping it on. But the 1128+25 is pretty solid if you want to go small and light.
Your Pelican case solution is plenty of protection, even for moderate off-road excursions and the accompanying light crashes/drops. A good friend of mine had a GS for a long while, so I'm pretty familiar with them. Pelican cases I'm very familiar with. If you have over 2" of foam around the gear, it's good for darn near anything you're likely to survive yourself... probably more. But weigh it all, because it may be too much.
If you want to carry a lot of gear and will be exclusively on pavement, you may consider something I've pondered repeatedly: a Uni-Go one-wheel trailer (www.uni-go.com
) that's rated for 110 pounds of cargo. For two-up travel I'd consider the trailer essential gear. Fantastically handy, too: I've watched someone unhitch it in about 10 seconds, then wheel it right into the motel room as it fits through a door!
An accessory I should have but haven't coughed up the dough for yet is an Epson P2000 or one of the newer variants. It's very small and light, but essential backup. So far I haven't ever lost any data, but I know I should be more diligent about it. I don't have the space, weight capacity, or frankly the inclination to carry a laptop.
You've got an outstanding pair of lenses to start with. To add a telephoto zoom I would still make the same choice: 70-300 DO. But if you can afford the weight and space the 70-200 f/2.8 IS lens is, of course, a little better and two stops faster. I've been very pleased with my DO zoom, though.
An extra bit of padding for anything sensitive to vibration or bumps is the fleece bags offered by Aerostich (www.aerostich.com
). They come in numerous sizes.
A bit off-topic, but I'm also an Iron Butt Association member: www.ironbutt.com
. They have lots of great motorcycle traveling tips, links, and a great e-mail list (LDriders) if you're looking for information in that direction, too.
Hope this helps. Enjoy!