I am 63 and have been racing formula for over 6 years. I have been windsurfing and racing for 24 years. I find formula challenging, but it also provides a lot of fun and excitment. It keeps me motivated to stay in shape. I have raced against Steve Sylvester on a few occasions and he is extremely proficient for his age. He is in a class ahead of me, but he probably has double the time on the water that I have.
I find that at my age, I don't carry the large sails in the winds that most formula racers do. Whatever they are on, I am usually on something 1-2 meters smaller. I do race with 11.0, 9.2, 8.4 & 7.6 race sails. I have even been on a 6.6 in 25 to 30 knots, so I do what I have to to have fun.
I weigh 79 kg.
Go for it - you will get a lot of bang for the buck.