Great idea.
I haven't written in a while, i have too little spare time right now.
Anyhow, i just wanted to add a suggestion. A more general way the predict mangos maturation time exists and it is the degree day method. You just need the degree-day for a given cultivar and you can foretell if something will ripen at your house or not, and, if it turns out that it will ripe, you can guess when it will ripe. You just need a climate table of your location with average temperature, and some very simple math.
It's pretty easy to build a degree day table for a given cultuvar (simply record the flowering date and the maturation date, do it for some years and do the calculation) but the best thing is that once you have the degree day for the given cultivar it is the same in Florida, California, Canary island, India, Italy, New York, Hawaii, giving everyone a rough idea on how long a cultivar takes before ripening in a given environment.