Weighht and Jockies

[Bill K]

Race 1 Aqu #8 Sunnybrook was 1.90/1 favorite. Stumbled and dumped Dominguez. Horse then last runs wide around the whole field and beats everyone to the wire by 5 lengths. Leading to questions:
1) does weight make that much of a difference in a horse's ability to run?

2) does the human on the back of a horse actually hinder a horses ability by dolling out its speed to supposedly conserve engery for the stretch drive?

Obviously I am not advocating racing without Jockies but it does raise an interesting question as to a jockey's effect on the results of a race?