Smacking the axle into the frame is about the worst thing that can happen. If it is doing that, then it will happen repeatadly.
Sooo. upgrading axles/springs WILL be better than leaving it as is. Every time the axle hits the frame, it is like taking a swing at it with a sledge hammer.
So if your frame is a lightweight frame, something must be done,
Did you know that axles can be custom built for your TT? Take the info off of the axle plate (a picture of it will do) and show it to a axle supplier. They can get you upgraded axles that will bolt right up... And it is not much more $$$ than buying an in stock axle.