I cannot see how this would be done without slight downhill assistance the whole way and over inflated tyres.
My e is going in for service on Saturday so I will soon tell if software is to blame (my car is a 2020 model registered 2021 on a '21). Best I ever get is 4.2m/kwh on a run. Rarely any higher than 4.4m/kwh on a short journey after already warm...
It may be worth plotting your journey on the various cycling trackers/planners which can give you good detail about the inclination of any journey.
May I ask the method of your pre-heating? Using the app or using the in car system, or the fob? I'm not sure I know the difference between cabin pre-conditioning or battery pre-heating. Are they the same thing?
Even if there is a boost to efficiency from the preheating, it must be short lived (First 10/20 miles or so until battery is cooled?) and at the cost of on peak tariff. Something to try when you need to do a 125m journey perhaps, but not something I'd try to aim for.
I can envisage the first honda e meetup - we all drive in convoy on the same day and conditions the same route, then compare notes at the end