So this is a topic that is worth a bit of attention (now that I'm finally getting to it).
As part of SRGW development, the WMData file was given a new function. There is a new line that looks like this in SR1914.WMData;
battstrdefault, 54.000, 38.000, 12.000, 45.000, 18.000, 40.000, 24.000, 24.000, 1.000, 18.000, 18.000, 18.000, 12.000, 6.000, 12.000, 1.000, 1.000, 1.000, 1.000, 1.000, 1.000, 1.000, 1.000
This line sets the default at a point in time. We added this because in 1914, initial tank battalions were deployed in very low numbers of tanks. In this case, 12. If you look in SR1936.WMData you'll find that the value there is 44.
The way the engine uses the WMData files is as trends. It does look ahead. So around 1928, a tank battalion might build to a strength of 30 pieces. When it gets to 1936, it would be at 44 pieces and would be stable from that point forward because ever other WMData file uses 44.
So, for Class 13, what should be the default sizes at each of 1914, 1936, 1942, 1949 and 2020?