I speculated when I first saw the mention of the Heirofalcon in the Dominator description at the back of Divided We Fall that just as the IRL Heirofalcon is related to the Lanner and Gyrfalcon the same could be true of the Mech, which could mean that like the other two the Heirofalcon is 55 tons. The HAG20 kind of makes me wonder if it's a birdified, omnified, slimmed down Shadow Cat II.