Is that Flywheel Energy Storage or Flat Earth Society?

I haven't found the gas motor I want yet for the 15kw output but I have lots of choices in the 8-10kw. Since this is needed much farther down the road, I have not put much detail design into it. I think I can build this for 25-30lbs. The JM1 only weighs 6 lbs. 10kw may be fine for me since who cares much if it takes 22 minutes to charge up during cruise versus 15 minutes.