Petr Polách writes:

We have a guy in the Czech Republic that attached this to his
Combat (with propeller) and has been flying with it like you do with Mosquito
motorized harness. He attached it to his keeland the thing has been maintaining
altitude after launching from the hill.

Gerolf Heinrichs does a calculation:

What a great idea. The problem is simply the power output. Here a
simply calculation. If your takeoff weight on a hang glider is about 130kg~1300N
and your sink rate is about 1 meters/second it means you would need thrust power
of 1300N*1m/s=1300Watts. That would seem quite doable, even with a rather shitty
motor arrangement, right?

The problem is the efficiency losses. If you need 1300Watts to eliminate sink,
you will need about 3000Watts mechanical to battle the propeller efficiency, and
about 4000Watts to make up for the electrical efficiency.

So with a motor controller battery arrangement that can output 4000Watts
electric, you have a realistic chance to break even. If however you want to fly
out of an airfield a common minimum climb rate of 2m/s is called for (otherwise
you end up scratching out low over the unlandable for too long for comfort) and
3m/s is probably the better bet.
But lets stay with 2m/s climb - that is 3 times what you need for holding the
zero. Means in reality you would like to have 12kW of electric power.

Compare this to what Manfred puts on his electric trikes - I think he goes with
17kW for the single seater light weight trike which might have lift off weight
of about 160-180kg.