The original metal bumper usually is fastened a little tighter, I’ve noticed
All of our karts with plastic rear bumpers are left lose to keep them from binding ( you don’t want them tight )
But for cadet karts I don’t know how it will affect the handling being a smaller frame.
Best you can do is drive it with it tight, and then try leaving it lose next session, and see how your little racer likes it
Technically it should change something, as the old bumper is so tight
If anything the kid will be faster, as the kart frees up on the corners. But hey, give it a try and see how you like it.
P.S. When I say lose, I really mean lose, It should rattle up and down when you tap it with your fingers. My 2 cents Fast Freddy. ;)