Questions about slick
 

I know that bias slicks grow and radial slicks don't. But my question is how much does a bias slick grow in the 1/8th.
I am a bracket racer and I run a 28 bias slick and my car runs 6.70's. I am thinking about running the Hoosier 18210 which is 29.5.
with some rough math with no growth for either slick I get that I will be crossing at almost 300 rpm less.
So how much does a 28 bias grow in the 1/8th.