Try switching out the wheels to ones with more friction.
Are there skid marks on the ball? You arn't getting any spped increase because the increased speed is just reducing the amount the wheel can grip the ball. These factors just cancel so the ball kind of hits a point where it wont go any faster and go a greater distance.
I mean, just think about it. If the wheel is going faster, then it would have to grab more the pull the ball with it (Since the ball has inertia and resists the acceleration) All the wheels force is being imparted via friction, and you have reached the max amount of force the wheel can impart with the amount of friction you currently have.
Compression would help. Try those wheels that have that orange rubber blunt-spikey stuff on it. Lets see what those do to the ball before you even add more compression
