Ok here are few

... WIN % >= 20%
... UnitTab Rating >= 96
... has a 'C' beside its name
... has a 'D' beside its name
... Same Jockey

and oaksnaf's is correct but drop it down to 14 days, 21 days usually means they pulled up sore after the win (unless its a 1800+ distance, then they just need the rest ).

They all increase the results significantly.

Good Luck.