I presoak larger formats because I believe it causes the developer to enter the emulsion at a controlled rate while replacing the water put there by presoaking. I agitate during proesaok - I also like the antihalation layer out of the mix. I also agitate by rapidly inverting the tank back and forth and then a radial spin before clunking it down to knock out air for each 5 second agitation. I wonder if gentle agitation interupts the laminar flow of chemical and if it replenishes exhausted developer as well. I have never had streaking or problems doing this. The effect of presoak on accutance is an interesting idea. It would be interesting to try some identical sheets and if the difference could be detected. - Frank