No, use the same sight picture for both barrels. You will actually shoot the
lower barrel more (e.g., singles in skeet) because it causes a little less stress on the barrel/frame lock-up and the recoil is more along the axis of the gun (rather than above the axis) so the muzzle jumps less.
Part of what makes double barrels more expensive is that the two barrels must be regulated to have patterns that overlap AMAP - typically at 40 yds - but you are only out less than an inch vertically nearer or farther than that. If they don't shoot the same, return the gun. A buddy actually got Browning to replace a Citori he had in which the lower barrel patterned several inches (L or R??) of the top. The story (as I remember it) was that neither the super high rib, the upper barrel, or the lower barrel were in registration. The lower barrel was bad enough for amatures to notice.