Mad Malvina fought against a Horse . . . GalCom? StarCol? who had a Bloodname in a Trial of Possession using hovertanks IIRC- Maxim II?- where she ended up killing the other tank and maybe her driver. Honestly . . . the development of the Quadvee MIGHT have also been a outgrowth of trying to duplicate the Alexander Jorgensson Bloodname trial controls, because it is 2 individuals running the QV. ONE can do it (since the other can get injured IIRC) for a loss of function. So in the 3120s-3150s, might we see the 'Tank Warriors' getting a bloodname with QVs locked in veh mode?
Also the Horses had two shifts towards armor- in their founding with their Khan's emphasis and after losing Tokasha as a source of mechs. The first was a philosophy/pride angle while the later was about necessity . . . and around the time the Elementals really got going. Look at their last several Khans we know of . . . Fletcher (Elemental), Cobb (Elemental), Kabrinski (Elemental), and current Fletcher? (Elemental). They maybe the 'tank Clan' but they look suspiciously like the 'Elemental Clan' to me.
Someone mentioned the original Clan founder trials . . . IIRC the scanty details we get, those were not a series of duels but rather competency tests. Think of the current military's promotion program dialed up to 11 . . . PT test for physical fitness, marksmenship with small arms and weapon systems (ASF, mechs, armor) if qualifying, tactical problems aka field exercises, and probably even command tests. Soldiers who did not make the upper 5% (or whatever it was) formed the auxiliaries assigned to each Clan and were probably the source of 'other' DNA used in the first trueborn sibkos.