You say your tank was completely filled, if so, how did your solutions move around the tank during agitation? I have used stainless and Paterson tanks over the years but have always had lots of room in the tank apart from what the solution is taking up, in other words, I have never completely filled a tank and I suspect your problem with uneven development has to do with filling the tank to the brim! BTW, Patterson tanks work fine, if you are having problems they will be because of agitation mistakes.