Problems with indoor track surface

[tworrs]

Hi all
I have a slight problem with my indoor racing surface, its an indoor bowling club, and while the racing area is more than is ever needed , open all year, and has a bar, lol, there is one problem that is causing a slight problem with our "top level racers" , there is a slight softness to the floor, not much, if you push it with your finger, it might go down about 10mm, or even less, on top of this we put our carpet down aswell, we have also stopped using additive, for the sake of the bowling carpet, so my question is this
What can be done to improve grip
Softer tyres, harder springs
Any help would be great