TC6 13.5t gearing non boosted?

[RDG 40]

I am currently running on a very small tight track polished floor, what FDR should I be hoping for, its coming off a tad too hot for my liking

FDR at present 5.71 28/80

Can any suggest if i go to between 4.5 - 5.0 FDR or vice versa seem to see some conflicting info on here which i think seems to come down to track

thanks