the bikes handling will be best with the loads closest to the axis of the wheels.
desire to do the trip total dirtbag style, going on the cheap, who even needs panniers? just wrap everything in a big blue tarp and bungie cord it to the top of the rack, add some boards in the roll to lend support, and go!
you'll have a great time discovering your ideal packing method.
methods I have used, from ultralite, to light, to fully loaded with winter camping equipment, skis and ski gear.