very nice software... i don't understand anything to these calculations, for me it's just a hobby, but i like to learn and i've another idea...
- Why to not add an optional field for the weight of the truck?
- You could write some alert message, or recommendations, about what to do to make your motor cooler in the case of thermaling, or what do do in case of under/overgearing... you could preconise some solutions (i.e:"reduce pinion gear teeth number to prevent early warming") ??? I think you don't need more that 10 messages to help everyone to set their car correctly...

I really enjoy your work guy!