Don't forget that the water is travelling slower near the bottom due to the flow being disrupted from the rocks etc... so even with the weight "slowing down the drift" your bait/lure should be travelling the same speed as the water, assuming you have the proper weight. With too much weight your gear will be slowed down too much causing your bait/lure to drift ahead of your weight; or too little which will allow the faster upper currents to pull your bait/lure downstream, placing your bait/lure upstream/behind your weight. Proper boat control/speed while boondogg'n or side-drifting only compounds the variables - and in my opinion these are the main variables (along with good bait and river knowledge) that seperate the fishers from the catchers.