Some observations:

There has been an unusually high number of grass-raced horses running on poly at Keeneland; could it be that horses with good turf-strides are better suited to this surface? As a side-benefit, the "off-the-turf" races WILL stay full; good for betting, and good for track handle, which leads to----

Handicapping?? I have found (so far) it's best to evaluate a poly race as if it were a grass race; i.e., fewer wire-jobs, and more stalker-closer types.

Throw out any horse who hasn't raced or trained on poly, AND hasn't tried the grass. Lone exception: in maiden races, give horses with strong grass pedigrees a long look!