Well the first two tanks would be roughly the size of the British Mark V tank with the TH-12 being somewhat bigger and the TV-4 being slightly smaller. 

Then of course the VB-1 is essentially a slightly larger, steam powered version of the French Char B1. 

So I guess if were using the average size of the steam tanks based off the example picture above, Arkil tanks would be on the smaller side (with only having a smaller profile as an advantage in comparison. And even then they aren't exactly hard targets XD)