God, your bike is going to be heavy! 10 kg for each box is a waiste of loading weight. Try to travel light! I drove through Australia on a XTZ 660 (2000) and had two alu panniers fixed to a steel frame. Even managed to sqeeze a small tool box in the pannier frame. It worked well but including my tent and my girlfriend everything became all pretty heavy.(15 kg for the panniers each, and 10 for the tent and camping gear). Thank god my girlfriend was light ;-). Too heavy anyway! It can be done though, but it will limit your moving ability.(more like driving a Honda Goldwing). Now I'm travelling light. Just a 45 ltr. bagpack put in a strong waterproof ortlieb bag and strapped down to the back of my seat. It works perfect. I gave up on bringing many spares. These bikes are very good and won't have any troubles (engine wise). Just change a few parts which are worn down like trottle and clutch cables before you leave.
The only things I always take with me are:
-clutch and brake levers.
- innertubes and tire levers (will fit under the seat)
-a bit of electr.wire and iron wire
Alle the rest that will brake down can be repaired down the road or can't be repaired at all.
Is you stick to your boxes try to make te point of gravity as low as possible. Also make sure the boxes aren't to close to your legs. In case you have to put you feet onto the ground for e.g. paddling trough deep sand. It's easy to get your feet stuck between the ground and the corner/bottom of the box. People have hurt themselves this way. I hope you understand my explanation...:-)
Use only your bike frame to attach your pannier frame to. Also the footrests are a good attaching point.
about: 'surviving a drop". Don't make them to strong. If you crash or drop the bike, it's the panniers and its pannier frame you want to bend, not your bike frame!
The good thing about panniers is, you can use them as a chair, table, bike jack/support when changing tire etc.
take care and take the solution that gives you the most confidence.