Crunching some numbers

I've been crunching some numbers with regards to my Mustang from lasy summer....After having it weighed and calculating what I removed after the fact my race weight with the driver was 3040lbs last summer. The calculator shows 10.81 with 475HP (my dyno figures) and I ran that number a lot all summer foot braking. This year with the changes I'm expecting the race weight to be 2965lbs, I'm expecting the HP to be in the 600-625HP range so that's working out to a 9.92 - 9.79 if she'll hook on the 28 x 10.5's with the transbrake......I see a window net and more brake's in my immediate future if I don't wimp out and lift...LOL...I'm thinking traction will be an issue but the old heap might surprise me.