P&G Optimum Mass Model

[trebuchet03]

This has been on my mind for awhile now...

So I just started to develop a model to look at how mass plays a role in P&G and see if there's any optimum for mass.

I started to tinker in excel a few minutes ago, and quickly realized that it will require some numerical methods to accommodate for aero resistance (as it's a function of time). For coarse resolution (like 5mph increments) - it shouldn't be too difficult when done in excel

So, other than RR and Aero Resistance - what other factors should I include in this model?