Look, here is a mini bike speed calculator, It's gonna be close.
http://www.csgnetwork.com/minibikepotentialspeedcalc.html
The tc is a good start. I wouldn't change the rear sprocket until that is installed and you have run the bike around for at least a little bit. I believe most people go ahead and add a 60 tooth rear sprocket at the same time.
My bike and I weigh about 360 lbs. 180 and 180. Well since before Christmas and New Year.
. I have a 47" wheelbase. That puts my butt torwards the front of the rear tire. I'm running a stock 212 predator with only the throttle screw backed out. Using a chinese tc with the driven spring in the middle hole, 8 tooth driven sprocket and 72t rear sprocket, for a 9:1 ratio, 19x7-8 tires. Top rpm is around 4000.
I started out with 10 tooth/60 tooth sprockets and worked my way down. One sprocket change at a time.
With that gearing, tires, and rpm, my top speed is around 27,28 mph. That is after the tc belt has shifted into the aprox. 10% overdrive which turns that 9:1 into about 8.1:1 final drive ratio.
Even with the rear axle behind me, I can still pull the front tire off the ground a little bit on a full throttle launch at about 2500 rpm, and if I slide just a little backwards on the seat it will stand up. But I'm hitting a little flat spot between the launch till about 3000 rpm. Between 3k and 4k throttle is fairly responsive. Same with cruising, if I'm below 3k throttle feels a little sluggish, about 3 to 4 pretty good. I'm slowly working on that. Even the tc may need tuning.
Point is, nothing is engaved in stone. You are going to have to find out what works for you. Either more power, less weight, or lower gearing.