Height (text placement and size in general) can be changed with the FontExtents part of carcols. X and Z control the horizontal stretch/placement, and Y and W control the vertical stretch/placement.
X - How far the left side of the text stretches across the plate.
Y - How far the top of the text stretches down the plate.
Z - How far the right side of the text stretches across the plate.
W - How far the bottom of the text stretches down the plate.
To move the text up, you have to decrease both Y and W values. Likewise, to move it down, you increase both values. Same with moving it left/right - decrease for left, increase for right. I would recommend changing the values by two decimal places so that you'll fine-tune it better.
As for scaling, change the values of either X and Y or Z and W. Increase both X and Y to make the text smaller, decrease to make it bigger. Reverse for Z and W, increase to make bigger and decrease to make smaller. Alternatively, you can modify individual values to stretch the text however you want. Keep in mind, if X/Y is bigger than Z/W (or Z/W smaller than X/Y) the text will turn invisible.
I've already played with these options since I made my add-on license plates mod six months ago (planning to release a full documentation with the next update), so feel free to use the values in it as a reference.