. I dunno why you can't use 5wt or whatever if you are strong enough.
Have you tried swinging a 5kilogram anything? That's 11lbs one handed with the weight mostly at the head. Sure you could swing it, but you would have zero control and no chance of hanging on to it if it hit anything. Not to mention you're going to tear out your rotator cup and any tendons in your elbow and wrist.