Originally Posted by Honu

Sure you can , people seem to like smaller gallop people for the most part in the west, but back east they dont care if you are 165 lbs as long as you can gallop a tough one. To me size doesnt really matter for galloping horses, if someone "rides light" per say and can think "horse" then it doesnt matter what they weigh . For working horses lighter is better in most cases but some big strong horses a heavy work rider can be a benifit. ( when I say heavy its all relative).
My boss is lucky that no rider in our barn weighs over 135 and they are all very good horse people.
If you have never galloped a racehorse before , you can simulate it with an english saddle by adjusting the irons , then my next suggestion would be to find a training center near where you live and start there.