"Tim" wrote
But while using the gas engine you're charging your electric motor system.
And I figure engine load would actually be a minorly questionable
concern, unless speed is configured into the equasion.

One of those laws of thermodynamics says you don't get any free lunch. To
recharge your battery, your engine has to supply as much energy to put into
the battery as your motor took out. Your engine normally converts gasoline
to noise and propulsion at a rate of X gallons per hour. If you add the
burden of producing charging current to its chores you'll use X plus
something. If what you mean about speed is that you don't have to put energy
back into the battery as quickly as you took it out, there's probably
something to be gained there. The question then is whether or not you break
even on the conversion losses.