From what I've been seeing with reaction at 4 is that the defenders obviously react a lot slower and i haven't seen linebackers and DB's jumping routes they have no right jumping. With coverage at 85 though I've been seeing defenders that are clearly beat, able to catch back up to the receiver way too fast, resulting in a lot of knock downs and sometimes sacks because coverage is too good. I'm guessing the pass coverage slider gives defenders a little extra speed boost to recover after getting beat on a route. So with that in mind i may try reaction at 4 and leave coverage at 40/45.