I am a big fan of this "movement" in the hobby. I always felt that there should be more coherency between the background of WH 40k and actual models.
There are different approaches to the process of enlarging space marines. Some people prefer to use terminator models as a base for tactical marines armor. Some people enlarge the actual gamin bases so marines look taller. Others use a plastic card to increase the dimensions of the stock model.
Personally, I combine the later method with sculpting. I feel that to increase the height of the model is not enough. You also need to increase the width of it.
My Mk III power armor that I used for my Blood Drinker sergeant is mostly sculpted. While I was working on it I tried to keep the "true scale" concept in mind. Below you can see this model next to the sisters of battle and regular marine.