I found some people have different calves too, I had to add an extra 15mm to a recruits armor I was building.
Always compare how you look to references, here you can see very little gaps between some troopers armor pieces, you don't want to take too much off
I would thread the height of the shins the same, with removing small amounts at time, it's easy to take more off but hard to put more back on.
A little heat on the base can also help spread the opening allowing the shins to come down over your boots and ankles, may be worth have a look at.