[CS:GO] Size Reference while modeling in 3ds Max?

I know models in source sdk can't be resized, which i hate with every inch of my being. When making a custom model for a map, how do you know how big to make it? Is there a height i could set a box to, to represent the height of a player? If so, how tall are they? I'm pretty new to CS:GO and can't make sense of exporting models, because i would really rather importing a character model into 3ds max, but i can't figure out how. Is this the usual way? Can anyone link me to a tutorial for this? If not, I could just keep importing the same model with different sizes to see which fits the best, but that sounds like a huge pain. Thank you in advance.