I think that its necessary to get pretty anal about your dosing process. Use whatever dosing method you want, but it has to pass this test: get out the measuring shotglasses and the stopwatch and make five double shots in a row. Stop the shots when they reach 60mL and record the extraction time. I suggest that you really need to have all five of those times fall within a four second window, otherwise you need to work on your dosing. How do you do that? Change technique and/or work on it more. Yes, you will be throwing out a lot of coffee, but in the scheme of things its $10 well spent.