[P-hack]

Ian, you have spent all your time and energy arguing semantics, over technology that is a moving target. You are here, waiting for my approval/permission/whatever to try to make a non-subjective/non-speculative/driver enabling series-as-most-efficient-more-than-2-percent-of-the-time point.

Asking me to correct all your errors sounds like a lot of work actually, more work than the analysis itself, not only because of all the mistakes you have made already (and evidence that you already ignore), but because the conclusion leads the analysis so it is bound to be biased and untrustworthy.

Here are my assumptions (because I have control over them)
1. Smart driver and/or automation, can target peak bsfc closely under acceleration, and best economy when cruising, and can glide.

2. More efficient gearbox and driveline, I think computer controlled sliding mesh is doable, not too much of a reach, far simpler mechanically, and more efficient. My job is to figure out the efficiency map for this component.

3. An efficient engine like the tdi, with broad rpm range in each efficiency band.

4. Some measure of onboard generation (this is f*cking obvious!!) as it has a battery and probably restarts frequently, the onboard generation can be increased to support climate controls and lights in the EV if regen is deemed too inefficient, but it is not meant to turn fuel into battery charge (until someone actually demonstrates the value of that proposition non-speculatively).

5. Similiar sized engine, though the pusher can be smaller since the EV still functions as an EV. It can be of sufficient size and ratios to get you home if you kill the battery, though at reduced performance as compared with battery assist. But since we are assuming a smart driver, it is conceivable that they would pick a smaller pusher that gives them just enough assist over their route that they get there with a mostly empty battery on purpose.

6. Conditions will be consistent with deliberate range extension (you have reason to hook up the "trailer" for this trip), and the driver has due influence over micro-conditions. Priority given to common usage.

7. EV can coast efficiently, and allows some coordination with pusher.

8. "luxuries", like imperceptable shifting, are not requirements.

Are you in a position to list your assumptions at least?

And some homage to costs is always appropriate, i.e. I am not going to make impossibly thin gears out of unobtanium and/or associated unobtainable manufacturing processes.