I took the average of a man briskly walking, in the manner that the stick war units do, and found that in 30 minutes they could achieve 2 miles. I used a stopwatch and timed a Swordwrath briskly walking with no stop from the spawn to the enemy statue. Here I found it takes approximately 30 seconds for a Swordwrath to cross the map. I divided 2 miles by 30 minutes, got 0.0666 repeating, then divided THAT by 2. With that I received a total of 0.0333 repeating. Then, I transferred this value into meters, and found that the original grasslands for Stick War is 53.64479999463552, or better rounded to 50 meters long.
Obviously, this is approximate, but now we have a solid length to go on, so we can complete our data for the original Stick War units.
(Also, I found that the original Stick War usually does not show damage numbers, but if a unit hits a giant, the values oddly show up. With this, I can also calculate damage, and possibly even unit HP.)