Here is a chart I made for myself to help quantify the difference.
I use it by looking at where I start, ie. at 30% length (3 in the left column), and I figure out how much I'm going to add on to the shape to bring it closer to the template, so if I go to 60% (6 in the left column) a change of 30%, I get a 44% improvement on the Cd (44% in the far right column).
I hope it's not too complicated. The tool helps me figure it out better.
