No, the roll center is the total measurement. So 2mm in front will just be the riser. 3mm in back is the 2mm riser plus 1mm shims. The Towers I'm using are the BMI towers. So it'll be the middle location on there both front and rear. Droop is measured above ride height. 5mm ride height plus 3mm droop will be 8mm on the ride height gauge. Then use the Schumacher gauge to make sure both sides are even.