I keep seeing this talking point brought up every year, I know some people assert that a horse that has won all his races carrying 118-120 are "negatively impacted" when they have to carry 126 lbs (though mathematically this doesn't make much sense) and others would assert that the added weight doesn't have a negative impact on ability (other than the TG computed relative weight difference, of course).

Has anyone ever done a fact-based study of figures to prove (or disprove) either assertion? Do horses carrying 126 for the first time run worse TG numbers?