Grind and dose are closely related, many use the 5 cent test to get into the ball park then fine tune from there. "Correct depth of the coffee puck is a whisker away from the shower screen at lock in" suggest you try the 5 cent piece test, fill the porta filter, tamp and place 5 cent piece in the centre top then lock PF in, if the coin is pushed into the coffee reduce the dose a little, the object is to have a gap between the tamped coffee and shower screen approx the thickness of the 5 cent piece. 🙂"