Yes. I managed legal cut off speed up this hill with my hub motor bike at age 61, I am quite fit with strong legs. 3.8 km long and 2.3 km long with bits over 15% coming back up the steep side. I calculated that I was providing over 120 W to achieve that speed.
You sound like a strong cyclist, you should manage. But... Forget about the no sweating bit of e-biking, you are going to be providing serious Watts, this is real sport! I don't think your desired average is realistic but hey, surprise us. Good news you will go faster downhill because of the extra weight of the bike!
Tips:
- always be in the right gear even with a hub bike
- ride at just under the cut off uphill to always have some assistance, say 23 km/h
- cheat... set the cut off to maximum motor speed which is about 32-33 km/h with your typical hub motor. You will be using lots of battery now so take that into account
- buy a much bigger battery than you think you need, see above
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