This year we are continuing using the US Sailing Portsmouth Yardstick rating system. This system can be used as a single point rating (D-PN number) (like PHRF) or a multi-point (rating changes with wind speeds) rating system. I do not believe a single-point rating system can be remotely accurate; boats perform very differently in different wind conditions. A multi-rating handicap system is a bit more work for the race committee, but our races are not that long to worry about drastic wind changes. Every race, race committee has discussions on the wind strength and direction.  We do have ananonometer and digital display on the committee boat (donated by Davis Marine Electronics) as well as some phone apps that will record average and max wind speeds. This year we are also making some rating adjustments based on performance. Like most rating data bases, they are only as accurate as the data submitted. For myself, when evaluating a boat's rating and performance, I look at the sail condition first. If someone feels their rating is off, they better have new sails and a good two years of data. Basing a boat's rating off one or two races is not valid. Luckily, with about 20 races per year, we get some very accurate data. We are working on a page or link that will list the rating changes for this year. On the changes, we have done an "across the board" change with the wind ratings. Monitoring and applying changes for each wind range is very time consuming, but I'm sure we have some data analysists that would enjoy this type of challenge. We are one of the clubs that submit our results to US Sailing to be inputted in their database. 

Here is the link to the US Sailing Yardstick Handbook: http://www.ussailing.org/racing/offshore-big-boats/portsmouth-yardstick-handbook/  Which may not load if you are not a US Sailing member. I am working on linking a pdf from the website. This handbook describes the rating method and the factors applied.