Hi - I just posted this on my blog but you probably don't read that - so here it is again.
I've created a spreadsheet based off of Bob Brant's Build Your Own Electric Vehicle and John Bidwell's Secrets of El-Ninja. I used BYOEV for the required torque formulas, and I used El-Ninja for the available torque formulas (they were presented as a nice short list in the Bidwell book!). I used the co-efficient of drag and frontal area figures from the defaults on the electricmotorcycles.net calculator (http://electricmotorcycles.net/modules/toolbox/battery_worksheet.php)
You can see the spreadsheet at: http://www.editgrid.com/user/jdh2550/CB-72V - if you want to use it yourself then you can get a free edit grid account (takes 5 minutes to setup) and do a Save As ... and create your own copy because you can't edit this sheet directly. BTW, the graph is on the summary tab and all the gory details are on the calcs tab. The other tabs are all work in progress for my CB-72V conversion.
Look it over and let me know if you think any of it's flawed (such as the coeff of drag figure).
If you want I can save this as an Excel spreadsheet and clean out my CB-750 bits and post it to the Download library.
It even produces a pretty graph (what more could you want?).
I hope you find this useful.