Fine-tuning the speed mod

I'm using the speed-reduction mod that reduces unit speeds by increasing the 'friction' caused by the movement over each type of terrain.

IMO there were two problems with unit speed. One was that all the units moved too quickly. That problem has mostly been resolved with the terrain/speed mod because it affect every unit to the same degree.

The second problem was the RELATIVE speed of units. Infantry were almost (and still are) as fast as cavalry, and that relative speed issue isn't resolved by the speed/terrain mod. Now, with the slower movement and killing speeds, I'm able to observe this problem more carefully. So, has anyone figured out how to affect the speed of one unit (or type of unit) and not another? It may be able to be done with the terrain mod too, I just don't know the details and whether that file distinguishes between the different kinds of units (Infantry v. Cavalry, etc.).