I had assumed that the new iZips performed some intricate wizardry to attain 20mph motor only and 28mph with "hard pedal assist" ...
After further research ...turns out this is readily and simple to match.
1st clue was the 350w motor.
350w is is the necessary motor output to sustain 20mph.
My previous models demonstrated that upping the voltage and limiting the current provides an extended shallow watt output curve, rather than the central bulge of power from a full current motor.

After a bit of searching I matched a possible torque curve ...



While technically true, the 28mph requires nearly 500w of pedal input.
500w of pedal input is equivalent to 23mph pedal only effort.