Hi Scottie
I am finding out, that it depends on the revs your engine makes it's Torque over.
Once you know this then you will have a better idea for your starting point and making your final decision.
My 2 stroke is a relatively Low Power/narrow Powerband combo so it is very very gearing sensitive.
There are two of us running Suzuki 250 RGV engines in different Classes down here in OZ, I'm APS the other is MPS and we share info. I had issues, but the MPS Bike ran well and went 131mph. A one tooth smaller Rear Sprocket was fitted and got an unexpected drop in Speed. It did not make sense based on our info leading up to the event
We did not have any Higher RPM Gearing.
After looking at the results of 2013 we found something we did not even think of,
the calibration on the Tacho was reading about 600rpm more than actual RPM .
After much head scratching and Forum Trawling we stumbled across some info about Tach accuracy mmmmm...As we have very limited data Logging capabilities on these Bikes, but run the same Aftermarket Ignition, we did a comparison between the Zeeltronic Ignition Monitor Reading against the Tach and found the same variation on both Engines. This explained what was happening, given the Narrow Power range we are playing with, why the changes had the wrong result
. The MPS Bike was indeed Maxed out at 131 given the Conditions and the Tune.
So this year I am running the same Engine Tune as 2013 and the other Bike has had some changes made to the engine. But now we know the Tach is wrong, I will be using my re set Zeel based Shift Light as the Peak RPM guide during the Runs and I'll be making any gearing changes accordingly. The MPS is an unknown at this point.
I am doing Tuneups in incremental stages year by year. I have done the same Calcs that you have and then I saved up and got the options so I could juggle front and rear combos within the theoretical Top Speed/RPM range once I knew what the next level Tune gave me. I am lucky that I have a a number of Sprockets available but I did have to get one Rear Sprocket made to fully cover things.
I am also looking at long term/$$?? at changing the Primary Drive Gearing as well if I ever get the Mythical 80hp RGV Engine Tune
So you can get it close and then go from there, but until you Run and find those Weird Dumb things well it is all part...
Pete