So you’ve enjoyed an unfair age advantage all of these years and now you’re complaining that the tables have turned and you are stuck with an unfair weight disadvantage? Boo-hoo-hoo. Deal with it. Your competitors have been doing so all the time you’ve been “at the front on a national level.”
If you really love karting you’ll just have to accept the fact the you’re not going to win for a few years. If what you love is winning using an age advantage, maybe you can switch to baseball and find a little league that will believe you’re 12 years old.
Okay, so the above paragraph is a little strong, but it’s written by a 6’2″ 190 lb. 57-year-old who has to go toe-to-toe with 20-year-olds of the same size and weight. Life ain’t fair. Just go as fast as you can and love doing it.