Hi -
The handicap range (ie. "rating") for the race is usually in the race title, but as you say not always present. Another alternative if you are looking to filter by races that are restricted by handicap range is to retrieve the top rated horse (since all the official ratings for runners are included). This is usually the same as or close to the actual range for the race.
However, we will look at adding the rating in its own field in the advance racecard data to make it easier to filter.
What other advance racecard data are you thinking of that you would like to see included? Mostly you can derive this information, but if you let us know we can look at it for the next release of Smartform which is coming up shortly. (please answer by commenting on this answer)