Once a week I do a trip from home to work 162 km (100 Mile). During cold winters here in Denmark thats the range of both battery and 9 liters petrol (high speed and 22C/72F). I can charge at work so this question is not a major problem to me.
I would prefer that I could somehow decrease the RPM (rounds pr minute) on long distances when I need the whole battery and whole gasoline tank.
It would make it more quiet - the REX engine makes some noise at 120-130 km/h (75-80 miles/h) - If I could start the engine once possible and have it working at lower RPM while the battery is also decreasing a bit at the same time. You can barely hear the engine when going 90-100 km/h (60-65 miles/h) probably due to lower RPM.
Is it somehow possible to do a hack and keep the RPM controlled lower. Both noise and fuel economy might even be better when the engine is working at lower RPM than maximum.