Is fast50s the only company that makes a stock size chromo frame? i want to keep my 50 a "50" if you know what i mean, and im not very big so i dont need a extended frame.
Frame braces work OK If your only worried abuot flex. But you also have the fact that the mounting point for the swingarm pivot bolt mushrooms really bad. That can only be fixed with a stronger frame. Ive also seen shock mounts bust off and bend bad which is from using the stock frame as well.
I worry about frame braces because they add stress to the motor mount . I would go with the fast 50's frame strongest stock chromemoly frame on the market.