Personally (It might have already been said) would be to spread some of that weight to the front. Maybe get a frame bag made up and a top tube bag for the heavier items you might bring. There is an array of new ideas rather than sticking with the traditional x2 panniers on the back.

Stick with the principal of taking less! You'll be glad after the first couple of climbs. I've got a pizza rack on the front which allows me to attach panniers and bungee cord a few things on top, Tent (MSR x2 Hubba) and stuff it in a nearby dry bag if it rains. When you sopread the weight the bike will become more responsive, as mentioned above when its all at the back the bike will rear up a little on steep climbs.

You'll figure it all out. Pack it up, go for a ride and amend where necessary.