CI Hack, dont know the answer but I suspect from your question that you dont understand the rating system. It is a disadvantage to them to have the lower rating on wed nights. The higher the number the more time faster boats would have to give them and the less time they would have to give slower boats. I think 84 may be the standard 36.7 configuration for one design and allows the standard class #1 headsail. When sailing some phrf they can get a credit for smaller headsails or weight, I think.
Actually it had to do with sail size. You would be correct if they sailed at a lower rating with the same sail. I hardly think that is the case. To be perfectly clear I a almost positive that 84 or 87 is with a 155% headsail and 90 is with a 145%. YRA LIS members can view certificates and the copy that was given to me shows a distance rating of 87 and L/W of 90 with +3 for 145% and +3 for max weight of 1500 pounds.
Ok, so It sounds like you are saying they are doing it right.Sailing with a larger 155 and a lower rating (84) and when using the higher rating they sail with a 145.
it also sound like they are getting a credit +3 for weight at some regattas and the distance rating of 87.